Akulap User Manual for room acoustics ISO 3382 - Dr-Jordan
Contents
1. Dr Jordan Design Report reverberation time DIN3382 Information for room and setup Room location and description Room capacity Description wall and ceiling Number of persons escription movable items Temperature and relative humidiby Measurement equipment Sound signal Measurement points reverberation time RT60 in 1 3 octave bands RTD im i 51 _ 014 200 025 T 250 013 500 Oir E a gH ao 0 14 T i 2500 O16 00 3150 018 x aD Ix Wo Ox Ik E E T frequency Hz 5000 0 21 reverberation time wide band 83Hz to 9600Hz RT60 T20 0 16s The measurement is ready AkuLap www dr jordan design de Page 14 Dr Jordan Design Since we did not configure any information for the measurement the info section 1s blank To complete this start the room manager from the menu Plugins gt room manager reverb Page 15 positions sound source 1 1 microphone DIN 3382 3 io s sm Namefesist MIC 1 LS 1 F date 18 4 2015 17 08 Datel System restaurieren Room location and description Description wall and ceiling PO Number of persons Description movable items Haunrvalumen Temperature and relative humidity Measurement equipment Sound signal Measurement points Responsable organization Press the E button AkuLap www dr jordan2. Files tC Dokumente und Einstellun Ji Q Suchen V7 mm 4 7 e frequency Hz 1000 1250 1600 2000 2500 3150 4000 5000 6300 2000 ier s os fase fos Your loas ose az Joa Joao ozo ewm o p je m ele m 6 hob reverberation time im 1 1 octave bands frequency Hz 125 250 500 1000 2000 4000 s000 IRT T20 s 0 24 16 0 16 n6 ni n9 o 20 error index 4 2 zm m faa fa Speech intellizibilityv STU RASTI C Tess sos oo on anne ont snos ize f um jm jm ue m m TAE fe fn pa o fa om fos om fa o fos 1 98 0 97 fase TIT TT ol Jos loss 10 00H logs Sone losi 2 fs m bo ta mo ta oc c H EH j A E Blt So wj io wj gu j m wo fo To Co a e c wu ca I a mu 2 2 2 2 ce c km Ch ea c ta o La elemelzua T t H H DO O c SO ce Il Il E m E m m Cn c oss nes oss oss ne oss nes os om os o oss os D gereret 2 2 2 2 E GI e Oo e m all es excellent enters FASTI O97 excellent detailed results esults as PDF file he eo 83 AkuLap www dr jordan design de Page 13
3. Dr Jordan Design AkuLap Professional Audio Measurement System www dr jordan design de User Manual for room acoustics ISO 3382 Dr Jordan Design t 1 www dr jordan design de 3348 1 JL omoi j lelml ab wr uit alai e ECL w A 1 i 2 0 a pE n 3 0 r 3 3 2 3 8 3 T E NN EE 2011 Dr Jordan Design AkuLap www dr jordan design de Page 1 Dr Jordan Design Preface Modern acoustic measurement systems such as AkuLap offer a variety of sophisticated methods of measurement These processes are very complex and require normally a long term training Therefore AkuLap has automatic measuring methods which allow measuring reliably many acoustic parameters by non specialists The experience of our designers and acousticians has been summarized in this automated system The goal 15 to require as little as possible user interaction At the same time we can prevent operator errors For experienced users we have many advanced features even for very special use cases The measurement results are written in a clear report Therefore you can print this report to easily archive or send them by email In this Quick Start Guide the most important information is summarized For more information please refer to the general guidance of AkuLap or the advanced literature Warning This analysis system can generate many synthetic signals With inappr
4. NX Ih Bequency ez reverberation time wide band 83Hz to S600Hz RT60O T20 0 16s Now this document contains all the information you entered AkuLap www dr jordan design de Page 7 Dr Jordan Design 4 Tips and tricks It is very important to measure the diffuse sound only The sound source should be omni directional The measurement microphone should not capture the direct sound of the loudspeaker In addition the excitation sound level must be significant higher than the ambient noise For a reliable measurement please note the following hints e The ambient level must be as low as possible Sources are open windows air conditionings PCs etc As long as you are yourself in the measurement room please be as quiet as possible e The loudspeakers must be adequately dimensioned to reach sufficient sound level Normally you will need large subwoofers for low frequencies 20Hz 100Hz e The sound of source should be omni directional Frequently special loudspeakers like dodecahedra are used But you can also try with several speakers simultaneously For low frequencies this 1s not critical at all since the wavelength 15 very long e The microphone should record the diffuse sound field only The microphone should not head directly to the loudspeaker e Repeat the measurement at different locations to get the average room reverberation time Measurements at single positions can vary significantly AkuLap www dr j
5. sow 36 125d6 l E You should now avoid any ambient noise Once you pressed OK Akulap waits for the trigger signal Start your shot impulse etc Akulap will start processing immediately After a few seconds your internet browser will open and shows the measurement results AkuLap www dr jordan design de Page 11 Dr Jordan Design Ansicht Chronik Lesezeichen Extras Hilfe Measurement of reverberation tim X files iC Dokumente und Einstellun C Q Suchen ir Besse Se nem P Measurement of reverberation time summary report room Office section 5tandard measurement MIC 1 LS 1 saturday April 15 2015 17 06 57 Aku Lap 035 PRT BOT 20 0 22 0 20 time s 0 a x 0 0 rill ani tn ik dk k 1k 10h 100 frequency Hz reverberation time 83 3Hz to 9600 0Hz RTOO T20 0 16s error index 13 Room low cut frequency V 1000 0m 23 1Hz For frequencies below this cut off frequency the soundfield contains modes It is not difuse For frequencies below this cut off frequency the soundfield contains modes It is not difuse definition x At the bottom you will find a link for detailed information and the formatted PDF document AkuLap www dr jordan design de Page 12 Dr Jordan Design Datei Bearbeiten Ansicht Chronik Lesezeichen Extras Hilfe Measurement of reverberation tim X 9
6. IR sre FR GD mimm il EUR amplitude i i T 1 7 0 200 400 600 800 1k 1200 1400 time ms Dr Jordan Design Ready 44100 32767 743ms Blackman With such linear display we can monitor this impulse response up to 600ms Therefore it is more useful to use a logarithmic display which 1s called Energy Time Curve ETC We can clearly see the linear decay for the diffuse part 5 File Edit Options Plug Ins DSP Wizards Presets Overlays ASIO View Windows Help Easy Measurements time ms Or Jordan Design Ready 44100 32767 743ms Blackman The most important plot 1s the Schr der plot Energy Decay Curve EDC which 1s the basis for reverberation calculation In this example we selected a range from 5dB to 45dB as a basis for calculation of RT60 For this example we get a wide band reverberation time RT60 of 1 3s AkuLap www dr jordan design de Page 23 Dr Jordan Design Unbenannt amp 3 File Edit Options Plug Ins DSP Wizards Presets Overlays ASIO View Windows Help Easy Measurements 0 253s 13 92dB D 07ms 0 00dB reverb time FFT progress time ms 32767 743ms Blackman 5 1 3 Measurement There are four methods to measure the reverberation time Excitation with impulsive signals shots explosives hand claps etc Excitation with bursted noise Excitation with pseudo noise sequences MLS Excitation with pseudo noise sequences Log Chirps 5 1 3
7. p e 3 i Diffuse reverberation Level dB Time Reflections within 50ms from the main sound wave are not recognized as echoes by the human ear Instead they improve they increase the overall listening quality Echoes are noticed after 100ms for single clicks or more than 1s for music If you have a typical diffuse reverberation the level decays linearly in a logarithmic display Therefore it is easy to determine the decay constant According to DIN IEC3382 RT60 is the time until the level decreases by 60dB AkuLap www dr jordan design de Page 20 Dr Jordan Design Diffuse reverberation Level dB Reverberation time RT60 5 1 2 1 Noise Level In typical rooms we have a noise floor air conditions PCs traffic etc from 30 dB to more than 60dB Therefore we would need very high levels 100dB to 130dB to measure the decay down to 60dB Diffuse reverberation Noise level Level dB Reverberation time RT60 Time In most cases the decay is measured to a lower value significantly above the noise level e g 32dB and then extrapolated to 60dB 5 1 2 2 Critical distance The distance from a sound source at which the reverberant sound is equal to the direct sound A very reverberant room has a short critical distance while an acoustically dead room can AkuLap www dr jordan design de Page 21 Dr Jordan Design have a much longer critical distance Outs
8. 1 Excitation with impulses With this method the room 15 excited with an impulse The resulting measurement signal at the microphone is directly the room impulse response Theoretically the excitating impulse needs to have an infinite level and an infinite short duration Such a signal is called a Dirac impulse In real world such signal does not exist You can approximate it with explosives pistols sparc gaps or balloons filled with explosive gas It is the goal to excite the room to oscillate at maximum level Loudspeakers are not suitable for that purpose because they can generate impulses at low levels only This method 15 simple and is one of the oldest techniques to measure room impulse responses On the other hand it 15 quite dangerous due to the high signal levels The microphones must also be able to handle such signal levels On the other hand the sound source radiates in all directions from a point source The following example shows the time flow of the sound level after a pistol shot of caliber 6mm The background noise has a level of 50 60dB The shot reaches a maximum of 125dB which is limited by typical measurement microphones The usable dynamic is 60dB Within 300ms the levels decays by 60db This is a small room with high attenuation which limits a diffuse sound field AkuLap www dr jordan design de Page 24 Dr Jordan Design WinAudioMLs shot_6mm wst E File Edit Options Plug Ins DSP Wizards Presets Overla
9. design de Dr Jordan Design Enter all the information Room location and description H Description wall and ceiling pee Number of persons rome Description movable items pue were open Haumvalumen Yum Temperature and relative humidity 2i E Bs Measurement equipment V2 3 Microphone MTG MY 10 Interface amp Sound signal Sines weep Chirp S0Hz 12kHz Measurement points 3 measurement points See attached layout map Responsable organization Dipl Ing Alex Thomas Thomas Acoustic Service It date Saturday April 18 2075 17 20 54 section positions sound source 1 microphone DIN 382 3 1A a 0 00 m sel X Name exist MIC 1 L5 1 date 18 4 2015 17 06 Aus Datei System Cancel restaurieren AkuLap www dr jordan design de Page 16 Dr Jordan Design Report reverberation time DIN3382 Information for room and setup Room location and description Office first floor Schanzenstrasse 27 01097 Dresden Room capacity 30m Description wall and ceiling Wallpapered with woodchip wallpaper Number of persons Room was empty Description movable items Curtains were open Temperature and relative humidiby 21 C 55 Measurement equipment EM MTG MV 210 Interface ATD 2 Loudspeaker Fostex Sound signal Sine Sweep Chirp 80Hz 12kHz Measurement points 3 Measurement points See attached layout map reverberation time RT60 in 1 3 octave bands Jn Lar a uo
10. T from the preset menu Akulap will show some basic summary of the measurement Welcome to the easy measurement wizard This step by step measurement wizard will guide through to the measurement of reverberation time This measurement requires the Following steps 1 Connection of the microphone 2 S lection of path to store the results 3 Optional calibrating 4 Start of Ehe acoustic shock with pistol ballon etc All other parameters are sek automatically Press OK The measurement manger will appear AkuLap www dr jordan design de Page 7 Dr Jordan Design positions sound source 1 0 microphone DIN 3382 3 1 8 o oo m sel Name does not exist MIC 1 L5 1 show PER MW configure Measure background noise Cancel Enter a new room with room new we Luxe Manager Please enter a name Far the new roam E fficel cancel _ AkuLap www dr jordan design de Page 8 Dr Jordan Design section positions sound source an microphone 1 DIN S382 3 EIL mum Don se a Eai Mame daes not esist MIC 1 LS 1 i configure Measure background noise Cancel For this first measurement there 1s nothing else to configure in this manager window Simply Room size mak reverberation time f Standard 14 Cancel Small hall 29s Midsize hall E Bz Large hall church 11s Select a rough estimation for the reverberati
11. dr jordan design de Page 4 Dr Jordan Design 1 General Description With this compact measuring system you can perform a wide range of acoustic measurements in a simple way The system consists of a computer and one measuring interface that you connect via USB Depending on your requirements and you can connect high precision type approved measurement microphones e By using the PC environment you get a large user interface e Short learning curve e Measurement results can be quickly and easily exported for documentation as a graphic or table e Modular system You can use different vendors manufacturer for measurement microphones e Modern computers provide high computing power The functions are available for advanced analysis Today measurements are possible which could not be offered so far in this price range 1 1 Features e With the large display it is very user friendly compared to classic hand held sound level meters Simple measurement of parameters according to ISO 3382 e Supports measurement via impulse noise or sinus sweep LOG Sweep Chirp Includes wizard for fast and easy measurements Training phase is very short Automatic error detection Generates reports HTML PDF according to DIN 18041 ISO 3382 Database manager to organize the measurements Average of different measurement positions simple export to Excel Measures RT60 with 1 3 octave resolution Import and Export of room impulse respons
12. es from to wav files Schroeder plot EDT T20 T30 Clarity and definition STI RASTI and STIPA IEC 60268 16 AkuLap www dr jordan design de Page 5 Dr Jordan Design 2 Room acoustics The reverberation time 15 the most widely parameter to judge on room acoustics This time in most cases RT60 measures the duration until the sound level in a room decreases by 60dB after the sound source has been shut down 2 1 1 Requirements for reverberation measurement To setup a complete system for room acoustics you will require the following components Akulap with Laptop Tablet Measurement microphone Tripod for the microphone Omni directional Loudspeaker with amplifier Optional sound level calibrator For measurements of the reverberation time a sound level calibrator 15 not required But this unit with its reference level helps to identify and document e g noise sources In addition you can verify the measurement chain with one step 2 1 2 Basic procedure A measurement requires the following steps Positioning and setup of loudspeakers and microphone Optional calibration of the microphone Automatic measurement and report generation Repeat the measurement for different positions Average all results Final report generation es M adi i am All other settings are configured by Akulap itself Therefore you will require little training only All measurement results are written into an comprehensive HTML PDF repor
13. he impulse response This impulse response 1s the base for all other calculation The reverberation time 1s based on the Schroeder plot AkuLap www dr jordan design de Page 26 Page 7 Dr Jordan Design Example impulse response 7 WinAudioMLS room wst E File Edit Options Plug Ins DSP Wizards Presets Overlays ASIO View Windows Help Gala sg 30 THD IMb 0 max avel Cursor time 0 225 level 0 0000 peak time 25 86m level 0 0015 FFT progress 44100 16384 372ms Blackman AkuLap www dr jordan design de Dr Jordan Design Derived Schroeder plot with selection rectangle Z WinAudioMLS room wst E File Edit Options Plug Ins DSP Wizards Presets Overlays ASIO View Windows Help Cursor time 0 2122 level 31 81dB peak time 0 01 ms level 0 00d6 reverb time FFT progress 44100 16384 3z2ms Blackman 5 1 3 4 Correlation with Chirps Log Sweep Measurements with MLS are widely used since they allow measuring fast and efficiently On the other hand there are some disadvantaged which required more advanced methods Very sensitive to distortion Very sensitive to frequency shifts pitch Equally distributed spectral density Distortion effects are difficult to hear In the area of room acoustics it 15 important to have sufficient sound energy compared to the ambient noise Therefore loudspeakers are often operated at their power limit which causes distortion Such distort
14. ide rooms with free field propagation you will have an infinite critical distance 5 1 2 3 Equation from Sabine For many rooms the reverberation time 7 can be estimated by the famous equation from Sabine T 0 163 A V is the volume of the room and A 1s the effective absorbing area This equation is valid only if the absorbing area is small with respect to the total area S This can be seen from a small example Let us assume the walls are absorbing perfectly This would lead to a reverberation time of 0 because there are no reflecting areas In this case the equation from Sabine computes a finite reverberation time which is wrong 5 1 2 4 Recommended Reverberation Times Rooms have different requirements for their reverberation characteristics A classroom should be optimized for maximum speech intelligibility with a short reverberation time while concert halls for classical music have a much longer reverberation time to improve the overall impression of music Recording rooms studios 0 65 0 8s 0 35s 0 55s Concert halls AkuLap www dr jordan design de Page 22 Dr Jordan Design 5 1 2 5 Example Room Impulse Response Below you will find an example impulse response which was measured from a small concert hall fS WinAudioM inbenc r x amp File Edit Options Plug Ins DSP Wizards Presets Overlays ASIO View Windows Help Easy Measurements zc BET an i mue a om im Sojan morj mem
15. ion appears with MLS similar to noise Therefore the usable headroom is reduced To reduce such distortion large loudspeakers are used which are operated in their linear area Chirp measurements are much less sensitive to distortion The size of the loudspeakers can be reduced which 15 very attractive for mobile measurements MLS signals have a constant spectral density white by design For real world measurements this 1s not the optimum for loudspeakers since most of the signal energy 5 located in the higher frequency area Let us assume the total amplifier output is 100W in the area of 20Hz to 20kHz The signal energy in the area between 10kHz and 20kHz is 50W AkuLap www dr jordan design de Page 28 Dr Jordan Design 47W are located in the range between 500Hz and 10kHz Only 3W are located in the lower frequencies between 20Hz and 500Hz This distribution is not suitable for typical loudspeakers since their power rating reaches the maximum at lower frequencies The constant spectral density of MLS may easily overload the tweeters Filter may be used to shape the spectrum but this technique 1s complex and has other disadvantages Chirp signals decay with 3dB octave This is similar to pink noise although both signals sound completely different The main signal energy is in the low frequency range which fits the best to typical loudspeakers With Chirp signals you can define an lower and upper frequency limit Signal energy is on
16. ly generated in the desired range and requires no complex filtering or shaping since MLS sounds like noise it 1s very difficult to hear distortions which may indicate an overload state for your loudspeakers With Chirp signals you will mostly hear when loudspeakers are close to their limit and reduce the volume But of course you can easily damage your speaker with Chirp signals With MLS you will in most cases destroy the tweeter with overheating with Chirp you can destroy the woofer with mechanical overload Therefore please adjust the volume carefully Unfortunately at high levels Chirp sequences sound very annoying in contrast to the monotonic MLS The measurement procedure is very similar to the MLS measurement First the impulse response 1s computed All other parameters are derived from that AkuLap www dr jordan design de Page 29
17. on time AkuLap www dr jordan design de Page 9 Dr Jordan Design DIN18041 Art des Raumes f Musik t Sprache f Unterricht t Sport eine Spartgruppe f Sport 2 mehrere Spartaruppen Haumvalumen 1 Uu rr i Anzeige der Grenzwerte mit Publikum Raum ist besetzt Wahlen Ste Abbrechen um die Aichtwerte nach DIN18041 NICHT anzuzeigen Cancel This dialog configure the limits according to the german standard DIN18041 Press cancel to no display any limits for typical rooms Enter the frequency limits settings frequency range mir 100 Hz mas 8000 5 Hz gave reset Cancel Press OK if you modified the settings or cancel to continue AkuLap www dr jordan design de Page 10 Dr Jordan Design 2 Akulap Licensed to Dr Jordan Design Demo Version Schanzenstrasse 27 01097 Dresden File Edt Options Plug Ins View Windows Help TEE cak ave E Signal Statistik LCegq LAeq 1 dB LAeq 38 6dB LCeq 40 6dB M cursor L Fmax 42 7dB frequency 144 56Hz LCpeak 53 406 value 44 1308 LASS dE m LAFteg L4eq 1 8dB frequency 48 3Hz LAFteq 40 906 value 2b 33dB time inband level 39 606 35 57V THO H progress The background noise has not been measured After this dialog box the program waits For the impulse either From balloon shot hand clap etc 1k frequency Hz z
18. opriate signal levels you can easily damage your equipment e g loudspeakers or your ear Therefore always start with low signal levels and increase the volume carefully Wear ear protection AkuLap www dr jordan design de Page 2 Page 3 Dr Jordan Design Cru AT IBI AQUI 666666666666666 LL Toa 1 121 a 2 1 1 Requirements for reverberation measurement 2 12 Basic procedure 2 1 3 Measurement techniques IQ AU M TDS WINE WICKS E Reverberation background information ccce 5 1 1 Definition s Basic theory 5 1 3 Measurement AkuLap www dr jordan design de 1 2 Room acoustics 3 5 Dr Jordan Design AkuLap is a professional tool for powerful real time signal and system analysis By using the PC environment it is not only a cost efficient replacement for classical laboratory equipment AkuLap offers more powerful features combined with a comfortable user interface Typical applications are acoustic measurements room and building acoustics and noise monitoring If you run Akulap on a notebook or even a tablet PC you can easily build a mobile measurement system Akulap can use many different front ends In most cases you will have the most advanced setup which consists of a Laptop and a USB measurement microphone e IF 7E 2m why teenies Th AIL AkuLap www
19. ordan design de Page 18 Dr Jordan Design 5 Reverberation background information 5 1 1 Definition The reverberation time is one of the most important parameters in room acoustics This parameter indicates the time after the acoustic energy inside a room 15 below a certain threshold after switching off the sound source RT60 is widely used which is defined to be the time after the acoustic energy 15 below 60dB 5 1 2 Basic theory The sound wave starts form its sound source and moves in all directions A measurement device will notice first the direct sound THHHHHHHHHHHH If a sound wave reaches a surface some part will be reflected according to the law of refraction Other part will be reflected in a diffuse manner Other part will be exciting the surface itself structure borne sound Other part crosses the obstacle and will be radiated on the other side Some part will generate heat Therefore the total sound level decreases AkuLap www dr jordan design de Page 19 Dr Jordan Design The number of reflecting components increases with the time while their level decrease Finally we reach a diffuse sound field where the sound arrives virtually from any direction The level decreases exponentially and will be linear in a logarithmic display The reverberation time 15 the decay constant Early reflections s d s l 9 9
20. t which you can print or distribute It contains in addition to the measurement results also the original impulse response for later analysis 2 1 3 Measurement techniques There are the following methods to measure the reverberation time Excitation with impulsive signals shots explosives hand claps etc e Excitation with bursted noise e Excitation with pseudo noise sequences Log Chirps AkuLap www dr jordan design de Page 6 Dr Jordan Design The direct method with impulsive signal is the easiest technique because we do not need a loudspeaker Therefore we recommend starting with this method Even simple hand claps are sufficient for small rooms For advanced measurements we recommend the Chirp method Bursted noise should be used only for historical reasons 3 First steps We start with a simple measurement via impulse First place the measurement microphone connect it to the PC and start Akulap 8 Akulap Licensed to Dr Jordan Design Demo Version Schanzenstrasse 27 01097 Dresden Akulap t E pec CM A y t CALIAVG SE LAeq i re LCeq LAFmax LCpeak LAIS LAFteq LAeq dB LAFteq 93 siens 4 sete i ee 4 spectrum x 2 xa eS os Loudness sone STFA ISO 532B TA L rm Preset longterm audio monitor iw Hide window automatically 1 1k frequency Hz Dr Jordan Design Z vl Slow 1136 125dB Select SHO
21. ys ASIO View Windows Help Blackman 5 1 3 2 Bursted noise This method excites the room with noise via loudspeakers and switches of the noise source Both impulse and noise signal are broadband covering many frequencies Single impulses are not suitable for loudspeakers since they are limited by their mechanics With noise you can excite the room with much more energy The following picture shows the sound level while switching the noise signal You can generate such signals with the burst signal generator AkuLap www dr jordan design de Page 25 Dr Jordan Design WinAudioMLS room wst E File Edit Options Plug Ins OSP Wizards Presets Overlays ASIO View Windows Help Sg 3D THD IMD Or Jordan Design Ready Blackman This method 1s still simple and 1s implemented by many hand held devices Since any other noise has direct impact on the measurement high sound levels are required This requires special designed loudspeaker and amplifiers In addition this method is only used to measure the reverberation time and not the impulse response 5 1 3 3 Correlation with MLS This technique uses pseudo noise sequences which are radiated via loudspeakers The special sequences allow suppressing background noise Therefore you can use lower signal levels Loudspeaker and amplifiers can be smaller which is a key factor for mobile measurements By using mathematics correlation via Hadamard transform we can calculate t
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