Audacity compact - Libero
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1. 24 or 32 bit floating point Exporting of WAV AIFF data and via the optional LAME Encoder Library even MP3 files Spectrogram mode to show frequencies e Plot spectrum commands for a more precise frequency analysis e Mixing together of different sample rates and formats in real time As a mere audio editor Audacity does not offer any advanced features which may be known from so called sequencer programmes This means more specifically Aucacity compact 26 Introduction that MIDI data can indeed be imported and shown by Audacity but they cannot be edited replayed or saved However these functions are already planned for future releases www bomots de The functional range of Audacity 27 2 Setup of the programme After starting the programme Audacity 1 3 6 you will see approximately the following screen on your monitor It can vary slightly graphically depending on the operating system since the versions cannot be completely identical because of the different preconditions Audacity File Edit View Transport Tracks Generate Effect Analyze Help Heirs oe ea ete ole ks e PAA De 5 0 7 h 20 30 40 Programme after the first start Audacity opens with an empty project window by default and presents itself thereby top down as follows Bellow the title bar is the menu bar with the items File Edit View and so forth The different toolbars are located beneath Lastly you can see a timeline in the2. Aucacity compact 28 Setup of the programme upper area above the empty project window Below the empty project window there is the time and project rate bar as well as the status bar which shows the currently used frequency 2 1 The various toolbars The symbols of the control toolbar should be familiar to most of you from other audio equipment The Audacity Control toolbar Though some of these buttons have extended features in conjunction with the SHIFT key also known as the key used to type capital letters Function Pauses current recordings or playbacks To resume press Pause anew Playback starts at the current position of the selection cursor or atthe beginning of a selected section If you hold down SHIFT while pressing Play the image of the button and its function will change The track or the selected section of the track will now be played Loop play over and over loop play until you press Stop Play www bomots de The various toolbars 29 Name Function Pressing this button you will stop the current recording or playback If pausing was activated both Stop the foregoing action and pause will immediately be stopped Moves the cursor to the beginning of the project time LA position 0 Holding down SHIFT will mark the audio Al Skip to L i track section from the current position to the starting start i point of the project Moves the cursor to the end of the project Holding S
3. The edit toolbar Aucacity compact 34 Setup of the programme Copy VH ut Function Cuts out the selected section from an audio track The potentially remaining part ofthe audio track is shifted to the left and is attached seemlessly to the remains of the left hand audio track Accordingly the new audio track is shorter exactly the length of the removed part of the audio track Following clips will furthermore be shifted or not depending on the settings The settings can be changed via Edit gt Preferences gt Interface gt Editing a clip can move other clips The selected area is copied to the clipboard while the original audio track remains untouched The copied area can be pasted to other areas as often as desired Clipboard contents of cut or copied areas of an audio track can be inserted at the position of the cursor with this feature Trimming is the opposite of cutting Trimming deletes everything but the selected area The trimmed area keeps its position The selected area is replaced by silence The last editing operation will be undone www bomots de DS Fit ae selection u The various toolbars 35 Function This feature restores an undone operation This feature magnifies the displayed audio track This operation can be repeated until for example the single samples are clearly visible and can be edited with the drawing tool Causes the opposite of the feature Zo
4. and converted into a discrete value In the following figure every vertical line stands for such a sampling sequence www bomots de Sounds sound waves and digital audio 13 Sampling of an analogue signal The calculated value is allocated to the next raster value by rounding up or down The following figure of the measured and converted values shows clearly the disadvantages of this method The horizontal lines are here the converted raster values Aucacity compact 14 Introduction Amplitude Time Rounding up or down respectively of the measurement results to given raster values The difference between the calculated value and the next possible raster value displays the error of quantisation This error occurs because the sampled value of the signal does not always lie exactly on the given value of the used raster and therefore has to be rounded up or down This consequentially causes minimal divergencies of the digital signal in comparison with the original one The advantages of digitalisation are however obvious digital data is a lot easier to process and to handle does not underlie any aging process and moreover they can be copied as often as you want to without any loss in quality The data can furthermore be saved very efficiently in digital form through compression or be made available worldwide via the Internet www bomots de Sounds sound waves and digital audio 15 During digitising the ampl
5. pressure without distorting and are therefore very popular for live on stage use and for recording loud instruments such as bass drums and trumpets Another advantage is the fact that they in contrast to condenser microphones do not need any electric power supply A disadvantage however is the higher weight of the membrane which leads to an impulse repeating of lower quality and a longer post pulse oscillation This in turn has a negative effect on the frequency response which does not process more or less in line as 1t does with condenser microphones but usually declines in the lower and upper frequency spectrum Additionally the frequency spectrum of dynamic microphones themselves is generally lower than that of condenser and electret microphones Condenser microphones are typical studio or respectively speaker microphones If you want to use Audacity for example for podcasting a condenser microphone is recommendable They are virtually always used when a recording as accurate as possible of the original sound is desired A slight disadvantage is as previously mentioned that the condenser microphone needs supply voltage to load the membrane and the preamplifier This problem is often solved by using 9 volt batteries for on stage microphones while it is energised in studios via so called phantom power usually a 48 volt direct current voltage provided by microphone inputs Electret condenser microphones are a variant of
6. but will also help in many cases to achieve better results We shall cover a wider range of topics beginning with analogue acoustic waves and ending with digital audio recording Additionally we will also take a look at the compression of audio data and microphone technics in this chapter 1 1 Sounds sound waves and digital audio Sounds are sound waves which from a physical point of view form barometric variations which are strung together However only sound waves which can be heard by us humans with frequencies of about 16 to 20 000 Hz or 20 kHz respectively are called sounds The frequency indicates in this context how often the sound wave oscillates per second At the same time the frequency also defines the physical length of a sound wave The formula for this is Length of Sound Wave Acoustic Velocity requency The acoustic velocity is however furthermore dependent on the medium in which the sound wave moves Relevant properties are in this case the mass density and the respective temperature Sound waves cannot move in a vacuum due to the lack of medium In the air acoustic velocity is for example about 760 mph at 59 F and decelerates consistently with falling temperature Barometric pressure on the other hand has no effect on acoustic velocity even though this has often incorrectly been assumed Aucacity compact 10 Introduction Medium Temperature Acoustic Velocity 68 Fahrenheit 11 408 mph Exa
7. can only be connected to a standard sound card via adapter If you own a condenser microphone with XLR connector additional phantom power is moreover required which sounds cards generally do not provide It is therefore in this case obligatory to interconnect a separate microphone amplifier or a mixing desk between microphone and sound card USB connector Still relatively new on the market but downright handy because this kind of microphone can be connected directly to a free USB port on your computer Even the necessary electric power supply can be obtained thereby via USB www bomots de Via microphone directly onto the computer 21 USB 3 5 mm TRS connector 6 35 mm TRS connector XLR female XLR male The question of which microphone to choose can actually only be answered individually The microphone just has to suit the voice or instrument You can read long consumer reports and discussions about this subject in various online forums which can definitely help to make a buying decision Our advice is therefore First of all read consumer reports by ambitious users decide exactly upon the desired applicability and compare the technical specifications as well The Audacity forum available at http audacityteam org forum can also give you a good overview Those who have the possibility for example at a large music store a conferrer or the like should certainly test the various microphones beforehand Once yo
8. compression cccccscccsssccsssscssssccssssccsssccssscssescoees 17 1 3 Via microphone directly onto the computer ccccsssccssssccssssceessees 17 1 4 What exactly is Audacity aaa LIU 24 1 5 The functional range of Audacity ccccsssccssssccssssccsssccssssccesssceeess 25 2 SETUP OF THE PROGRAMME cccsccseeeseeeeeeeeees 27 2 1 Ihe var ous TOOID AT Si a un au aona aa 28 2 2 Serec ION Toolbar nun en 36 2 3 Computer EE EE 40 2 4 Calculating the computer latency cccsssscssssccssssccsssccssssccsessceeess 40 3 WORKING WITH AUDACITY cc ceceeeseeeeeeeeeeeeeeees 43 3 1 Opening and importing fIlOS ccccccccssccssssccsssccssssccsssccsessccssssceeess 43 3 2 Marking of audio tracks aussi sans ae 47 3 3 Editing audio tracks 2 aa aa au 51 3 3 1 Cut and delete with preliminary check 51 Aucacity compact 4 Table of Contents 3 3 2 EE EE KE 3 3 3 COD EE 53 3 3 4 EE 54 3 3 5 Ee EEN 56 3 3 6 Splitdeleie ann ker has naar east SCH 3 3 7 eS SAET e EE 58 3 3 8 elt GE 59 3 4 Command menu ENEE 60 3 5 Placing cuts EE E 61 3 5 1 UE EVN CW ge lee Se nee ee ee 62 3 5 2 Variable playback regonzg sranti 63 3 5 3 Finding zero crossings snenie ii iE ai REEE 65 3 6 The different tracks cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccceces 65 3 6 1 ae RAC KG sense ae ba ra ec a Sane bate ian A 66 3 6 2 IER e EE 69 3 6 3 kt tracker anne nee Te T2
9. differing recording levels 110 5 3 3 Recordings do not run eentred 111 6 PREFERENCES E 113 Gl Audo TVOne ee 113 6 2 E REI 115 6 3 Er rt Export tune a ais 116 6 4 SPECIFOSFANIS aaa sans 118 03 Directorios erno E a ul 119 6 6 Adjusting the programme inter face cccccccscccssssccsssccsssscessscoees 120 Or eweg e 123 6 3 WIOUSE SC OUD euer EE 124 Aucacity compact 6 Table of Contents 7 COMMAND LIST WEEN 127 7 1 IEN 127 7 2 Ee aE Te 129 7 3 CHEM 131 7 4 KT EEN 132 7 5 EE 133 TO ARAVA TE nun neunten 134 ele SIEB kamera 135 8 DOWNLOAD AND INSTALLATION cccecececeees 137 8 1 Ee 138 8 2 MACOS EE 139 8 3 Eege 139 8 4 Installing the MP3 Encoder ssccsssscssssccssssccssssccssscccsssceesscoees 141 6 GLOSSARY EEN 143 10 APPEND a E E 147 INDEX EE 149 www bomots de Foreword Dear reader In Taylor Hackford s brilliant movie Ray which is about the life of the musician Ray Charles the protagonist who had just become famous is led through the newly built up recording studios of his record label in the middle of the 60s of the past century A representative of the label shows him the for the time period excellent equipment and comments Totally state of the art Tom Dowd built an eight track mixing console When I saw the movie at the theatre in 2005 this scene amused several visitors which proves the enormous technical p
10. or communicating On the one hand this has very practical reasons for example to store a sufficient number of songs on a CD or with regards to telephony because it is simply cheaper to build a microphone or a speaker respectively which only records or reproduces a relatively small frequency range Here are some examples Medium Sample Frequency Channels Sample Frequency Range format AM Radio 11 025 kHz 50 5000 FM Radio 20 05 kHz 20 15000 16 bit DAT Recorder 48 kHz 20 20000 16 bit Audio DVD 44 1 to 192 20 20000 stereo or up to 16 20 or 24 kHz max 6 bit channels The development of digital technique finally brought the distinction between analogue and digital signals If you record for example analogue sounds like speech or singing with a microphone using a tape recorder the result will stay analogue The analogue signal can in this case take every possible value of a certain scale Aucacity compact 12 Introduction However if you save an audio signal via computer the signal will be digitised which means that it is converted into discrete that 1s integral numerical values The analogue digital converter and for the reconversion the digital analogue converter a d d a converter are hereby used which are both located on the sound card Example of an anlogue signal In this process which is also called quantisation the analogue signal is measured in certain intervals the so called sampling rate
11. perspective of the audio track With the aid of this device you can shift an entire audio track horizontally thus on the timeline For this purpose you drag the audio track by holding down the mouse button to the desired position Small arrows will indicate if parts of the audio track are moved into the negative time line Device which combines the different features depending on the image of the mouse pointer and position of application I Enables the positioning of the point of www bomots de The various toolbars 3 Symbol Name Function playback via mouse click and of the markings by holding down the mouse button A right mouse click zooms out the perspective whereas selecting while holding down the right mouse button fits the marking directly into the perspective E The mouse pointer looks like this at the margin of the envelope which you can then shift by holding down the mouse button By holding down the CTRL key you can shift audio tracks on the timeline A selected area can also be moved by beginning to move right where the selection starts To the right of the device tool bar you can find the meter toolbar Disable Meter Disable Meter SS SC Start Monitoring Vertical Stereo Hori j Vertical Stereo Linear i Linear Preferences Preferences Meter toolbar with menus Aucacity compact 32 Setup of the programme The individual commands of the menus Di
12. well as heterodyne frequencies or sequences with changes in volume such as low sounds which directly follow sequences of very high volume which the human sense of hearing cannot separate from each other or respectively cannot perceive The most important audio data formats for working with Audacity are discussed in more detail n the glossary at the end of the book 1 3 Via microphone directly onto the computer The first step of editing digital audio is usually the recording of language music and sounds via microphone All you need for direct recording of audios onto your computer is the programme Audacity a sound card and a microphone Mistakes which are made here at the beginning of the working process are typically hard or impossible to correct later on The recording itself and the Aucacity compact 18 Introduction selection of the microphone are therefore of crucial importance Let us begin with the microphones which can today be classified into three main categories e Dynamic microphones moving coil microphones e Condenser microphones e Electret condenser microphones variant of the condenser microphone These microphone types have in common that they convert sound waves via a mechanically oscillating membrane into an electrical signal Dynamic microphones convert via the movement of an induction coil within a magnetic field This is also called induction principle Dynamic microphones can bear enormous acoustic
13. 3 6 4 Ee A DE 74 37 SRECOP COUN EE 76 3 8 Working with Shortcuts ccscccsssccssssccsssscssssccssssccsssccssssccesssceeesees 76 4 EXAMPLES OF USE kee 81 4 1 Cut audio tracks via labels ua an a ERS ERRER SI 4 2 Removing background NOISES ccccssccccssccsssscssssccssssccsssccsesscsessees 84 co MRD Cen KEE a 87 5 1 AP Plane of CLIECUS ua u a aha 87 5 2 Standard Heels sslsilie 88 32 Fade WOUb En ae ser E EE 89 3 22 E ne 90 2 Bass DOOS EE EEN 9 5 2 4 CUNO ach ss artes eee ea ea RER SE 92 www bomots de 5 2 5 Fe QUAI EE 92 5 2 6 San Be EE EE 94 523 WV CE EE 95 5 2 8 Eeer 96 5 2 9 COMPFOSSOM 0 cc0cccssececastectassescesecrabestascescaseencdsedeseanecsercedeatenasecnares 97 52 10 Leveler ensen a Oa ioa 98 52 11 Nomales EE ion 98 5 2 12 Nyquist prompt 99 32 15 AE ee E ee 100 5 2 14 Noise removal cece cccccccccesccceeeecceeeeeceeseeeceeaeeeceeeeeeeeuenseeeaenses 101 32 15 Repair as ae 103 3 2 10 ARCVCUS Cis ee Ee 103 5 2 17 Truncate slencee 103 5 2 18 Change tempo ceccccccccccccseecccceeecceeeeeeceeseecceseeeceeseseeeeenseesaenses 104 5 2 19 Change pithy eege EES 105 52 0 PANU ee ee eae teas 106 322 VV ANN al os ie eat ee oa ae Sa eee cian ce 107 32 22 FRED CA ai ene ee eee ee ee ee 108 5 3 Problems and possible SOLUtIONS ccscccsssccssssccsescccsssccssssceesscoees 109 5 3 1 Recording with interruptions and disturbances 109 5 3 2 Recording has
14. Audacity 25 1 5 The functional range of Audacity With Audacity you can complete a lot of tasks Pay attention to the fact that you may possibly need additional devices or software for certain tasks and functions Thus for the already mentioned live recording of speech sounds or music you need for example at least a microphone which has to be connected to the computer via a mixing desk or directly via sound card The most important features are e Importing of different audio formats such as WAV FLAC AIFF AU Ogg Vorbis and MPEG data Importing of audio raw data Creating of an unlimited number of audio tracks Compiling live recordings Digitising of analogue data mediums like cassette tapes or vinyl records Cutting copying deleting and mixing of audio data Providing audio data with special effects such as changing speed or pitch of a recording Unlimited undo actions and restoring of work steps e Recording via microphone and other sources via the line in input like for example mixing desks or amplifiers and online sources dependent on the capabilites of the used sound card Recordings with a sample rate of up to 96 kHz and a sample and a floating point of up to 32 bit are hereby supported Changing and mixing of an unlimited number of tracks Deleting of continuous background noises Manual deleting of disturbances via the drawing tool Displaying of the recording level before during and after recording Recording in 16
15. PROFESSIONAL OPEN SOURCE AND LINUX KNOW HOW WOISIOWOO Markus Priemer Audacity compact q s e ry enoti e gt rv UA e titu i Professional sound processing with the best free audio editor Markus Priemer Audacity compact User Manual With foreword and contributions by Markus Meyer bomots Belax Linux und Open Sourc Taschenbacher Audacity compact All rights reserved This book may not be copied reproduced or transmitted by photocopying recording or in any other way in its entirety or in part without the expressed written consent of the publisher Likewise in accordance with the right of communication to the public prior consent of the publisher is needed to exhibit the book and its contents The publisher notes that the mentioned company and brand names as well as product trademarks are as a rule protected by trademark and patent laws Publisher and author do not guarantee the functional capability of the described procedures and standards 2009 bomots verlag Publisher Dr Holger Reibold Translation Heike Mieth M A Susanne Fahn M A Cover design bomots verlag Text design bomots verlag Cover Photocase Sascha Duffner Printing COD ISBN 978 3 9393 16 65 7 www bomots de Table of Contents FOREWORD ana 7 1 INTRODUCTION een 9 1 1 Sounds sound waves and digital AUCIO ccccsscccsssscssssccsssscssescceeess 9 1 2 Audio data and
16. and states that the sample range must be at least twice as high as the maximum displayable frequency R Maximum displayable Frequency eee The maximum displayable frequency in turn is geared to the recipient that is to the frequency range audible for humans Therefore a sampling rate of 44 1 kHz has been defined for CDs resulting in a maximum frequency signal of 22 5 kHz which already is beyond the human perception of maximal 20 kHz By using several channels it is moreover possible to produce surround sound which is not possible for mono recordings with only one channel Stereo recordings use two separated channels which can be output to a right and left speaker during rendering Even more channels are used for example on quadraphonics 4 channel stereophony or Dolby surround multi channel sound reproduction with five speakers and 5 1 audio with six channels If we take for example a regular audio CD At a sample rate of 44 1 kHz and a sample range of 16 bit as well as 2 channels for stereo effect the data rate is calculated as follows 44 100 16 x2 1 411 200 bit s Thus audio recording if uncompressed needs quite a lot of memory capacity A recording of three minutes in CD quality already needs about 30 MB disc space This equates for example to an amount of data of about 6 000 pages of text or to the capacity of more than 20 floppy disks Just a few years ago computers were simply overextended by these amounts
17. ction in which they are held while sound from the back is practically completely shielded Moreover their directionality matches aproximately the human ear which is why they are prefered for recording of ambient sounds e Supercardioid and Hypercardioid These polar patterns are in comparison with normal cardioids significantly more directed and can therefore supress background sounds significantly better Hence they are usually used for more distant acoustic sources such as movie and television shots where the microphone has to be outside of the display window Aucacity compact 20 Introduction 270 0 0 90 2107 90 180 180 Cardioid and hypercardioid characteristics Finally you should also pay attention to the right connector for the microphone or respectively remember to buy the applicable adapter Standard microphones usually use the following four connectors 3 5 mm TRS connector The so called miniature TRS connector fits every standard sound card as well as the outputs of every walkman or MP3 player But beware A slightly smaller 2 5 mm TRS connector for subminiature devices like for example Dictaphones also exists 6 35 mm TRS connector The big TRS connector is used for mixing desks keyboards and amplifiers An adapter will be needed for the connection with a computer XLR connector A popular connector for professional devices used for mixing desks preamplifiers and so forth It
18. egie Mellon University the programme has soon become an editor to be reckoned with for audio data of every kind since its introduction in 1999 The software is available for the operating systems Windows as well as Linux and Mac OS Aucacity compact Foreword By now Audacity has evolved from an insider tip to the probably best known software of its kind Ever since the release of the first version of Audacity the programme has been downloaded over 40 million times just from the official homepage alone Furthermore the software 1s available on countless download sites on the Internet and is enclosed on booklet CDs in computer magazines all over the world A google search for audio editor leads directly to Audacity s homepage Although Audacity in the meantime is not the only free programme for editing of audio data anymore many users who for example appreciate the easy and intuitional operability favour it to other similar applications Despite its popularity Audacity is still developed further by volunteers in their spare time I myself have been part of this pleasant team of dedicated software developers from all over the world since 2003 With this book we want to give you all the information you need to apply Audacity reasonably The author Markus Priemer made a point of giving you both an overview of the handling of the programme as well as a detailed description of every function Furthermore you will find interesting backg
19. for example the format hours minutes seconds was chosen selections may only start and end at integer seconds A format for video films such as hh mm ss PAL frames 25 fps has the advantage that the sound editing exactly matches the screen change so that frame accurate editing 1s possible This avoids furthermore needless clicking and other disturbances in the audio track which can occur otherwise www bomots de Selection toolbar 37 The format is changed for all three display ranges at a time no matter in which pull down menu the change has been set You can choose between End and Length as an indication in the second display while the third display Audio Position shows the current cursor position or allows its setting Project Rate Hz Selection Start Ge End Length Audio Position snap to r ponon eppes bon pg ang eg onge m33 es S000 16000 22050 44100 45000 HpUUU The selection toolbar To work completely accurately you can also edit the values directly in the selection toolbar For this purpose you click directly on the respective display with the mouse pointer and enter the desired value Small arrows indicate if parts of the audio track are moved to the negative time range Aucacity compact 38 Setup of the programme L i 2 Stereo 441 00Hz 32 bit float A 1 0 The arrows show that the beginning of the audio track is in the negative time range The follo
20. heless interferences or if there is a clearly audible hissing you systematically have to go through all elements of the recording chain test them individually if possible and where necessary substitute those components which could be responsible for the error But before you act blindly you should always test the wiring and the conducted settings first www bomots de Via microphone directly onto the computer 23 Recording from other playback devices If you have another playback device like e g an MP3 player or a CD player you can record its output signal which comes from the line out jack or a green jack via the line in input or respectively the blue jack of your computer The following colours are usually used for the different ports of a computer Colour Function Silver grey Side speaker output stereo Back speaker output stereo Subwoofer output and centre output Often alternatively switchable to the digital output Microphone input mono Speaker output line out stereo Blue light blue Line in stereo If you want to record from the output of another programme you should initially check whether the respective programme itself allows recording You can then edit the result with Audacity subsequently Many sound cards allow you to choose the entire output as the input channel Different terms are used in this context such as Wave Out or What U Hear Using this setting you can utilise Audacity
21. in amount of latency thus a certain delay Even f it is just a matter of a few milliseconds the processing of a signal also requires a certain time for its way e g to the sound card and from there to the speakers If the latencies are however too great certain works cannot be carried out reasonably anymore 2 4 Calculating the computer latency An optimal setting of the latency is necessary if you for example want to record and play an audio track simultaneously In the following we will try to find the optimal settings for the latency of your computer Pay attention to the fact that the preference Multiplay has to be activated in the register Audio I O and make sure to choose the right recording device e g Microsoft Soundmapper or use for example a wire between line in www bomots de Calculating the computer latency 4 and line out to be able to play and record an audio track at the same time Then execute the following steps e First set the display in the selection toolbar so that it shows millisceonds e Now choose Generate gt Click Track which opens the corresponding window and create a metronome like click track For this purpose you can keep the given settings and just accept by clicking OK e Now click on the record button and record the click track while playing e Stop the operation after a few measures via the stop button Depending on the quality of the sound card the audio signal is recorded more
22. itude or respectively the volume of the audio signal is sampled with a certain frequency and the thereby calculated values are saved The sampling sequencies which are executed every second are called sampling rate Audio CDs for example have a sampling rate of 44 1 kHz which means that the audio signal s sampled 44 100 times per second and the thereby calculated values are saved The second important factor for digitising analogue signals is the so called sample format or sample range It practically sets up the size of the scale or raster in which the conversion of the numerical values takes place and thus determines the number of possible increments The beforementioned audio CD usually uses a sample range of 16 bits with which exactly 65 536 different values can be displayed Sample Format or Possible Values Sample Range 16 bit 2 65536 Common sample ranges The higher the chosen sample rate the bigger on the one hand the memory requirements but on the other hand also the dynamic range that is the difference between the lowest and loudest sound For 16 bit stereo the dynamic range is for example about 96 db approximately 6 db per bit sample range At the same time Aucacity compact 16 Introduction a higher sample range reduces the quantisation error n relation to the original signal The Nyquist Shannon sampling theorem shows moreover the direct correlation between sample rate and frequency range
23. ive team if need be Audacity was originally created for a project at the Carnegie Mellon University in Pittsburgh USA which dealt with frequency analysis Dominic Mazzoni has been envolved right from the start and is still significantly supervising the project today He and an international group of volunteers organising themselves via Internet continuously develop Audacity further Audacity is written in the programming language C A special feature is the fact that Audacity has been developed for all three major operating systems Windows Mac OS X and Linux To provide a similar graphical user interface for the different operating systems the wxWidgets software library is used The latest release is 1 3 6 beta which has been launched in October 2008 and the latest stable release is 1 2 6 respectively which is recommended for efficient working Audacity enables the individual user to handle different tasks independently which previously could only be realised time work and price intensive at a recording studio Linked to an Internet connection and a website or respectively the access to the according Internet portal these products can be made available worldwide This development has already gained ground in the form of self recorded and mixed music audio blogs and podcasts and has enriched cultural life for a while In the following the latest release 1 3 6 beta will be described www bomots de The functional range of
24. kip to down SHIFT will mark the audio track section from the and current position to the end of the project After pressing the Record button a new track will be created Recording begins at the current cursor Record position with the set recording rate and can be paused by pressing Pause and ended by pressing Stop The tools toolbar which looks rather unimpressive is also important for the work via mouse and will be described in the following Audacity tools toolbar Aucacity compact 30 Setup of the programme The individual devices can also be chosen comfortably via keyboard since they are usually allocated from left top to right bottom with the function keys FI to F6 Symbol Name Selection tool Envelope tool af dee Time shift tool Multi tool mode Function By activating this device you can define the cursor position in a track via mouse click or mark a certain area via holding down the mouse button Using this device you can change the volume for a selection This is for example useful for fading tracks in and out manually Start by zooming in on the audio track until you can spot the individual samples as dots Holding down the mouse button you can now draw the samples anew This is for example useful for removing short background noises manually Allows to zoom in left mouse button or to zoom out right mouse button or SHIFT left mouse button respectively in order to change the
25. mples of acoustic velocities For humans the most important transport medium for sound waves is the air From a temperature of 59 F the following wave lengths exemplarily result Other frequencies can also be calculated easily with the aid of the beforehand mentioned formula Wavelength 21 25m 3 40 m 0 340 m 0 017 m 16 Acoustic Range of Humans 1 20000 Hz 10 100 1000 10000 Infr 1 KHz Intrasound z 15000 Ultrasonic Wavelengths of different frequencies Sound waves below 16 Hz the lowest frequency audible for humans are called infrasound These are probably used for communication by blue whales elephants and giraffes www bomots de Sounds sound waves and digital audio 11 On the other side of the scale in the range not audible for humans from about 20 kHz 20 000 oscillations per second to 1 gHz 1 billion oscillations per second the sound waves are called ultrasound The possibilities for the use of these sound waves are extremely diversified Thus ultrasound is used for instance in medical science as a diagnostic imaging technique or to remove calculus and to break up kidney stones It is furthermore used in seafaring for measuring water depths locating shoals and for navigating and in materials engineering for example for non destructive material testing But let us return to those sound waves which are audible for humans Many mediums are limited to a frequency range which is necessary for hearing
26. of data www bomots de Audio data and compression 17 1 2 Audio data and compression As you could see in the last chapter t can be extremely memory intensive to save audio files which is why different methods are used in order to achieve a compression of the data This saves memory capacity but also makes it possible to work more efficiently with the data Algorithms for the compression of digital data such as movies or documents search during this process mostly for repetitions in order to overwrite the area of repetition subsequently saving disc space Since identical repetitions in music are rare audio data does not lend itself easily to compression Most of the lossless compressors therefore use predictive encoding which first makes a prognosis of the amplitude and afterwards saves the actual difference to the prognosis The attainable compression nevertheless 1s strongly dependent on the respective audio data and averages at about 25 70 of the original while the lossy compression reaches a reduction of the data to about 10 of the original without audible differences in quality The most popular audio format definitely is MP3 which was developed by the Frauenhofer Institute in collaboration with the companies AT amp T Bell Labs and Thomson This procedure which in the meantime has qualitatively been outrun by other formats like Vorbis or AAC uses data reduction by leaving out not or hardly audible frequency ranges as
27. om in and demagnifies the view Fits the display of a marked area to the Audacity window Depending on the current perspective it will be zoomed in or out Fits the whole project into the window Depending on the current perspective it will respectively be zoomed in or out This feature is especially useful to give you a quick overview over the project as a whole To the right of the edit toolbar there 1s the transcription toolbar which offers the option to play audio data faster or slower Aucacity compact 36 Setup of the programme Transcription toolbar with input window Besides the slider which you can drag by holding down a mouse button via the mouse pointer you also have the option to open the input window Playback Speed by double clicking on the scale and to enter a value directly To play the current project faster or slower set the slider first to the desired speed The factor 1 0 hereby stands for the original speed The factor 0 5 stands for a speed reduced by 50 the factor 1 5 respectively for a speed raised by 50 Then click on the button with the green arrow on the transcription toolbar to play the current selection with the chosen speed 2 2 Selection toolbar Finally there is the selection toolbar below the project window The selection toolbar allows the setting of the project rate on the left side If the feature Snap to is activated it only allows selections in the chosen unit If
28. or less clearly The rendered audio signal is recorded slightly out of phase in a second audio track In the following example the signal first had to be amplified to meassure the latency 1 980 1 990 2 0 2 080 2 090 2 100 2 110 a DH U DH Li H DH Li D Li DH DH Li D High noise component and a latency of 0 072 seconds To measure the latency mark the beginning of the signal on the click track to the beginning of the same signal on the recorded track Now you can read the latency of your computer in the selection toolbar The above example used a standard installed sound card with a latency of 72 milliseconds Aucacity compact A Setup of the programme Latency Audio to buffer 100 higher more latency milliseconds Latency correction 72 negative backwards milliseconds Adjust the latency To adjust the latency you have to enter the calculated number as a negative number in milliseconds into the window Preferences register Audio I O under Latency correction Now you can repeat the above mentioned recording Both of the recorded tracks should now be synchronous to each other www bomots de
29. rogress of recording engineering in the past 50 years Nowadays we are able to produce recordings of music and language in excellent quality record them on compact disc or share them online with very little financial and technical effort Not only can users make their own recordings via microphone but they can also use existing material thus a song from the internet turns into a ring tone on one s own mobile phone a symphony by Mozart is embedded into one s podcast and the song of the favourite artist becomes a karaoke version for the next birthday party A whole generation of the Internet the Web 2 0 lives solely on the contents of users and their creativity thereby generating a culture of creating and re creating a cut and paste culture enabled by technology which releases unexpected resources of creativity as Lawrence Lessing American professor of law describes in his book Free Culture The Nature and Future of Creativity Part of this culture of creativity is the digital audio editor Audacity This programme which is published as so called open source software on SourceForge net and licensed under the GNU GPL not only allows users the free use and transfer of the application but also the inspection of its source code and hence the possibility to upgrade and adjust the tool oneself Developed by the original author of the software Dominic Mazzoni merely for process analysis as part of a project at the Carn
30. round information for example about microphone technologies as well as several step by step tutorials You are in good company no matter if you are playing in a band and want to edit your recordings with Audacity or if you use the programme as a journalist editor or podcaster to edit your interviews or articles It is clear A free software does of course not replace neither singing lessons nor the studies of audio engineering but Audacity is a tool with which people can express their creativity On this note I wish you a fun time and success while reading this book Yours Markus Meyer Markus Meyer graduated computer scientist was born in 1979 and has been a member of the Audacity Technical Leadership Council since 2005 which is responsible for the further development of Audacity He is CEO of a software engineering company and lives and works in Nuremberg Germany For further details contact Markus Meyer by e mail markus audacityteam org www bomots de Sounds sound waves and digital audio 1 Introduction The following introduction is intended for those who are not familiar with the basic terms and procedures n the field of audio techniques Only a very rough overview will be given which shall assist to get a basic understanding of the subject Basic physical correlations and related terms will not only help later on for a better understanding of the programme Audacity and the tasks which can be realized with it
31. s NTSC non This format works with 29 97 frames per second drop frames without omitting or dropping frames Example 00 h 02 m 48 s 29 frames NTSC frames Only counts the frames in a six figure display Example 002 481 frames hh mm ss PAL frames Displaying format for the European video standard PAL which exposes 25 frames per second Example 01 h 23 m 45 s 15 frames PAL frames 25 fps Counts PAL frames in a six figure display Example 025 832 frames hh mm ss CDDA Displaying format for audio CDs One second consists of 75 frames at CDDA At the same time one frame is Aucacity compact AQ Setup of the programme Format Explanation frames 75 fps the smallest sector which can be burned on an audio CD Example 00 h 01 m 27 s 08 frames CDDA frames 75 fps Counts the frames in a six figure display Example 018 481 frames At the lower end of the programme window there is the status bar which gives you various useful tips such as Click and pull to shift the left selection margin The individual areas and toolbars can be moved almost entirely user defined The serrated left edges are the respective parting lines To move a unit run the mouse pointer on the serrated left edges and move the unit to the new position by holding down the mouse button If you want to restore the original arrangement choose View gt Toolbars gt Reset Toolbars 2 3 Computer latency Every computer has a certa
32. sable Meter Disables the respective meter which is then displayed in grey Enable Disable Meter Enables or disables the input level meter microphone icon Horizontal Stereo Standard display which shows the meter horizontally from left to right Vertical Stereo Shows the meter vertically from bottom to top Linear Switches to a linear scale in the meter 0 0 silence 1 0 maximum level meter db Standard display which shows the scale of the level meter logarithmically 0 dB maximum level meter Further settings for this display range can be made via Edit gt Preferences gt Interface gt Display range minimum Preferences Here you can determine how often per second the display is refreshed Possible values are 1 to 100 Please bear in mind that a high rate requires correspondingly higher processing power Next you find the mixer toolbar below the control toolbar With its help the output volume is adjusted on the left and the input volume on the right The input source can be chosen via the right pull down menu www bomots de The various toolbars 33 Level control for output and input volume You can change settings by either pulling the controller to the desired position by holding down a mouse button or by opening the respective window by double clicking on the scale to directly enter the value The edit toolbar offers further important features for the editing and viewing of the audio tracks
33. the condenser microphone but they use an electret membrane which is located between the condenser plates for sound propagation This type of microphone is nowadays the most popular one because of the very compact construction and the low cost manufacturing and it can be found in many devices such as mobile phones interphone systems laptops baby monitors or even hearing aids www bomots de Via microphone directly onto the computer 19 One really important aspect is the directional characteristic of a microphone which provides information about how well the sound can be absorbed from different directions Some modern condenser microphones already provide a selectable directional characteristic as optional equipment Four basic characteristics can generally be distinguished e Omnidirectional These microphones absorb sound from all directions equally well This type of microphone is also called nondirectional and is mainly used for the recording of background atmosphere or in studios e Bi directional Microphones of this directionality are also called figure 8 microphones They are pressure gradient receivers which absorb sound from both the front and the back of the membrane Through constructive changes even cardioid characteristics can be reached 0 0 270 90 270 907 180 180 Omnidirectional and bi directional characteristics e Cardioid Microphones of this characteristic mainly record from the dire
34. to record sound while a different programme replays something Conflicts may occur in isolated cases because two programmes access the sound card simultaneously Using newer drivers or a different operating system might solve this problem Alternatively a temporary solution could simply be to directly pass the ouput line out green jack via wire to the line in jack blue jack and to record the input via Audacity from line in Aucacity compact 24 Introduction 1 4 What exactly is Audacity Audacity is a free and cross platform programme for audio editing Free does in this context not only refer to free of charge but above all free in terms of liberty This includes primarily the liberty to be able to use this software for all even commercial purposes The software may furthermore be copied circulated as well as adjusted to one s own requirements and demands Other distinct characteristics of a free software are the licensing under the GNU General Public License GPL which is also known as a free copyleft license for software and the fact that the source code is available for everyone The developing trend of such free software which is also called open source projects 1s directly dependent on the composition and interests of the respective team of developers as well as the requests and suggestions of the users Many teams however offer moreover individual enhancements of the respective software Simply contact the respect
35. u have decided on a microphone nothing will get in the way of making your first recording Here are some tips for successful recording e Initially adjust the settings for the recording level Regulate the sound level in a way so that the sound will be recorded as loud as possible but you absolutely try to avoid clipping e If applicable run a test recording of several seconds before the actual recording and check the result for possible interferences falsifications clippings and so forth e Try to eliminate or avoid background noises For indoor recordings you should for example locate a quiet room free from echo For outdoor Aucacity compact 22 Introduction recordings you could for example use a wind deflector against the sounds of wind mask flapping parts of clothing and turn off other disturbing sources beforehand such as possibly ringing mobile phones If you have background noise that you cannot turn off you should bring the microphone as close as possible to the source of sound which is to be recorded This way the background noise is at least recorded mutedly Recordings of speech should be carried out at a volume as constant as possible meaning without any outliers upwards or downwards When recording musical instruments you should familiarise yourself with the individual directional characteristics of that musical instrument to be able to place the microphone as optimal as possible If there are nevert
36. wing table explains the different time formats Format Explanation Seconds Counts full seconds in a six figure display Example 000 047 seconds hh mm ss Here h stands for hours m for minutes and s for seconds Example 02 h 16 m 34 s for 2 hours 16 minutes and 34 seconds dd hh mm ss For extremely long recordings this format additionally shows d for days This means that the display changes after 00 days 23 h 59 m 59 s to 01 days 00 h 00 m 00 s www bomots de Selection toolbar 39 Format Explanation hh mm ss This format shows in addition to hours minutes and milliseconds seconds also milliseconds Example 02 h 16 m 34 986 s hh mm ss samples This format divides the seconds into the respective samples To reach CD quality this means that every second contains 44 100 samples Counts samples in a nine figure display hh mm ss film frames A time and cut format which is suitable for film shots where 24 frames per second are exposed fps means frames per second Here the display 01 00 00 00 follows 00 59 59 23 film frames 24 fps Format for film shots with 24 frames per second which displays the single frames in six figures Example 073 396 hh mm ss NTSC drop NTSC productions use 29 97 frames per second To achieve this odd number NTSC drop frames initially work with 30 frames per second but then omit or respectively drop every 900 frame Example 00 h 02 m 48 s 29 frames hh mm s
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