to the FRI-100
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1. VV VV VV HUI IUAI COC OI UI HI IDOL UI TICIHEILO U UI TIT ULTRASONIC MICROPHONE AND AMPLIFIER FRI 100 USER S DOC 100 Rev 1 2 Copyright O 2013 All Rights Reserved Florida Research Instruments Inc 1980 North Atlantic Ave Stes 502 520 Cocoa Beach FL 32932 Phone 321 613 3862 Fax 321 613 3863 www floridaresearchinstruments com FRI 100 1 Ultrasonic Microphone and Amplifier FRI 100 1 Ultrasonic Microphone and Amplifier FRI 100 1 Ultrasonic Microphone and Amplifier Table of Contents Chapter T INTO UCI re ee O eb t da Semen eG 1 Specification i SI Lei M nn Requirements ihe A eee A Chapter 2 Hardware een HR 2 Chapter 3 Operation Example Rodent Ultrasonic 3 AppendX A ii A A iaa 6 Quantitative Analysis of Sound Pressure 6 Appendix B Contact Information 9 CHAPTER 1 INTRODUCTION The FRI 100 1 Ultrasonic Microphone and Amplifier accurately measures both the amplitude and frequency of audio signals in the 500 Hz to 100kHz range This device is suitable for measuring machine emissions vocalizations of mice rats birds or bats and many other paradigms More than a simple detector the FRI 100 1 produces an analog voltage output o2. sound pressure level at 1 m would be 0 0075 V 1 Pa V 0 0075 Pa Considering the large variation of sound pressure levels typically encountered and the need to multiply or divide to obtain sound pressure in Pa at one meter it is usually easier to calculate sound pressure using logarithms A standard system has been developed ANSI S1 1 1994 to yield a logarithmic measure of the effective sound pressure level of one sound relative to a reference value Thus effective sound pressure levels are measured in decibels dB above a standard reference value Sound Pressure Level SPL or sound level Lp is defined in ANSI S1 1 1994 as Lp 10log10 2010810 dB ref P ref Where pref is a sound pressure level reference value and prms is the root mean squared rms value of the sound pressure level for the measured signal DOC 100 Rev 1 2 Copyright 2013 Florida Research Instruments Inc NOTE Sound Pressure Level is often abbreviated simply as SPL Sometimes variants of the actual measurement unit are used such as dB SPL dBSPL or dBsp These variants are not recognized as units in the ANSI standard The unit dB SPL is sometimes abbreviated to just dB which can give the erroneous impression that a dB is an absolute unit by itself Keep in mind that SPL measures Lp are not absolute measures in and of themselves They are expressing one sound pressure relative to a rererence sound pressure The commonly u
3. 0 1 BNC connector to the National Instruments myDAQ device the center and ground can be screwed into the terminals Alternately Florida Research Instruments makes an FRI 2000 2 BNC adapter for the myDAQ to interface with a National Instruments myDAQ device NI myDAQ BNC Adapter DOC 100 Rev 1 2 Copyright 2013 Florida Research Instruments Inc FLORIDA RESEARCH INSTRUMENTS INC FRI 100 1 ULTRASONIC MICROPHONE AND AMPLIFIER 4 Plug in power supply and turn on amplifier The power supply has a 2 1mm connector and supplies 12V 500mA Insert the connector into the port on the back of the Amplifier and flip on the power switch FIQUre 5 4 vom ni Insert power supply connector to Power Input port 5 Select LPF or Direct Direct passes the microphone input directly to the DAQ LPF applies a low pass filter to the signal The LPF is an anti aliasing filter that attenuates signals above 100KHz The LPF setting is recommended Figure 3 aeatian nt Ihrartli DL Guntoh Direct LPF Switch DOC 100 Rev 1 2 Copyright 2013 Florida Research Instruments Inc APPENDIX A Quantitative Analysis of Sound Pressure Levels Unlike many instruments on the market the FRI 100 1 Ultrasonic Microphone and Amplifier is a specialized device that is calibrated to produce a defined signal amplitude in response to a standard sound pressure level Thus it is useful not only for recording the frequ
4. ation screw marked CAL This calibration screw adjusts the overall gain of the amplifier The FRI 100 1 has been pre calibrated at the factory DO NOT adjust the instrument gain if you will be using the FRI 100 1 to quantify the actual amplitude dB of rodent vocalization Refer to Appendix A for more information regarding measurement of sound pressure level amplitudes 1 Place the microphone in measurement location The microphone should be centered over desired location and pointing at the subject of interest As an example the picture in Figure 3 1 shows a typical setup for mouse open field ultrasonic vocalization Figure 3 1 Microphone Placed Over Cage Microphone Support Not Included DOC 100 Rev 1 2 Copyright 2013 Florida Research Instruments Inc FLORIDA RESEARCH INSTRUMENTS INC FRI 100 1 ULTRASONIC MICROPHONE AND AMPLIFIER 2 Attach microphone to amplifier The microphone jack is keyed and only fits one way Rotate until it slides in Screw the outer sleeve to the jack to prevent accidental disconnection Fiqura 2 2 Mirranhnna Cannacrtad ta Amnlifiar 3 Connect amplifier to Data Acquisition Device DAQ using BNC cable An example of a data acquisition system would be the National Instruments myDAQ The myDAQ is available at www studica com at a special price to students or faculty Other National Instruments or other manufacturer s data acquisition systems may be used For connection from the FRI 10
5. ency profile of rodent vocalizations but also it can provide an accurate measure of the amplitude or Sound Pressure Level of the vocalizations For researchers interested in quantifying the amplitude of vocalizations special consideration should be given to the calibration specifications of the FRI100 1 instrument as well as the physical layout of the recording environment particularly the distance between the microphone and the test subject To report standard Sound Pressure Levels Lp the level should be reported at a distance of 1 meter between the microphone and test subject However it is often inconvenient to configure an arrangement in the lab where the microphone is at a distance of 1 meter from the test subject Thus it is necessary to convert measurements obtained a distance of less than one meter to the equivalent measure that would be obtained at a distance of 1 meter Calculating the 1 meter equivalent sound pressure level depends on the expression of the initial measurement If the microphone output is recorded as a voltage the voltage expected at a distance of one meter is obtained by multiplying the measured voltage by the measurement distance in meters Example If a microphone placed 0 25 m or 1 4 m from the source produces a sound pressure level of 30 mV 0 03V the equivalent pressure at 1 m would be 30 mV 0 25 7 5 mV or 30mV 4 Recall that the FRI 100 1 has a calibration scaling of 1 Pa V Thus the equivalent
6. ll need to do post hoc scaling of your recording signals using some other data processing method e g export data from your recording system to an Excel spreadsheet NOTE if the signal generator output is set using the generator s output level control be sure to load the generator output with the proper load For example if the generator output impedance is 50 Ohms the output must be loaded with 50 Ohms In the case where the A to D being used has a high input impedance the stated generator output voltage must be doubled i e a setting of 0 5 V peak will produce a 1 V peak signal into a high impedance load Finally if a test signal of 1 V peak causes the output of the A to D to saturate reduce the amplitude of the test signal by a factor of ten to 0 1 V peak and replace the factor of 94 dB with 74 to compensate for the reduced signal level A note on rms values Expressing signal levels in rms equivalent values assumes an averaging over either time or space and is usually used to express the spread of a measurement The rms value of a single DOC 100 Rev 1 2 Copyright 2013 Florida Research Instruments Inc measurement is the measured value In the case of a pure sine wave the measurement is assumed to be averaged over a full cycle and is typically used to calculate the power of the signal For example a sine wave with an amplitude of 1 V peak measured across a 1 Ohm resistor will cause 0 707 Watts to be dissipated in the resisto
7. n the BNC Connector that is proportional to sound pressure level The analog output can be connected to third party data acquisition systems e g National Instruments Specifications The frequency response of the FRI 100 1 is linear 4 dB up to 100 kHz The analog output is 14 Volts The FRI 100 1 microphone and preamplifier combination are calibrated to provide 1 volt peak output into a high impedance load when excited with a 50 kHz ultrasound sine wave with a peak pressure level of 1 Pa or Lp 94 dB SPL 20 Pa 0 dB Peak levels were selected for ease of setting up associated A to D converters as the peak value could be easily related to the full scale count of the converter This calibration is independent of distance from the sound source and reflects the actual sound pressure at the face of the microphone The output impedance of the FRI 100 1 amplifier is 50 Ohms and must be considered when connecting the unit to other measurement equipment Notes 1 The high impedance load assumed for calibration is high relative to 50 Ohms and the loading effect of low impedances must be considered For example a 500 Ohm load has an error of less than 1 dB while a 10 000 Ohm load has an error of less than 0 05 dB 2 If the A to D has a 50 Ohm load the sensitivity is reduced to 0 5 V peak due to the drop across the FRI 100 1 internal impedance Many instruments have a fixed 50 Ohm input impedance so the input impedance of your rec
8. ording hardware should be determined if your goal is to make quantitative measurements of vocalization amplitudes in dB Requirements Third party data collection hardware and software DOC 100 Rev 1 2 Copyright 2013 Florida Research Instruments Inc FLORIDA RESEARCH INSTRUMENTS INC FRI 100 1 ULTRASONIC MICROPHONE AND AMPLIFIER CHAPTER 2 HARDWARE The FRI 100 1 includes a Microphone and an Amplifier A power supply is also included which provides a minimum of 12V 500mA The brand and type of power supply depends on the user s country The FRI 100 1 Ultrasonic Microphone Figure 2 1 is designed for sound waves in the 500Hz to 100 KHz range Figure 2 1 FRI 1nn 1 Micrnnhnne with Fynladad Viawe nf Connector and Microphone The amplifier on the FRI 100 1 is calibrated to provide a relatively flat frequency response for the microphone 4 dB from 500 Hz through 100KHz It uses a 12V 500mA DC power and outputs the signal to a BNC port Figure 22 ERIL100 4 Mirranhnna and Amnlifiar DOC 100 Rev 1 2 Copyright O 2013 Florida Research Instruments Inc RIDA RESEARCH INSTRUMENTS INC FRI 100 1 ULTRASONIC MICROPHONI CHAPTER 3 OPERATION Example Rodent Ultrasonic Vocalizations Two output settings are available DIRECT and LPF The LPF setting allows you to apply a low pass anti aliasing filter to the output signal with a cutoff frequency of 100 KHz The front panel also has an access for the calibr
9. r as the rms voltage of a 1 V peak sine wave is 0 707 V For more complex signals such as a rodent vocalization the rms value must be computed by averaging the square of the vocalization over a selected duration and then taking the square root of the result if indeed the energy put into the vocalization is of interest Analysis Example Rodent Ultrasonic Vocalizations Inexpensive software Raven for analysis of rodent Ultrasonic Vocalizations is available from http www birds cornell edu brp raven RavenOverview html National Instruments offers a number of software sound analysis packages or the user could write an application in LabView www ni com References 1 http en wikipedia org wiki Sound_pressure Sound_pressure_level APPENDIX B CONTACT INFORMATION Please contact Florida Research Instruments Inc for information regarding any of our products Visit our website at www floridaresearchinstruments com for contact information For technical questions email info floridaresearchinstruments com or karlzum gmail com DOC 100 Rev 1 2 Copyright 2013 Florida Research Instruments Inc
10. sed reference sound pressure level pref in air is 20 uPa rms which is usually considered the threshold of human hearing roughly the sound of a mosquito flying 3 m away Most sound pressure level measurements will be made relative to this level meaning 1 Pa will equal a SPL of 94 dB 20 log 1 Pa 0 00002 Pa 94 dB If a sound pressure pi is measured at a distance ri one can calculate the sound pressure pz at another position r2 using the fopowing quation m Ta M Converting the resulting pressure to Sound Pressure Level in dB allows the correction for distance to be accomplished by simply adding logarithms 20 log p2 20 log p1 r1 r2 20 log p1 20 log r 20 log r2 In the case where r 1 meter L 1 meter L ri 20 log r rigure A r wA MS AT CIEL IAN v i TAY OTO V Inne THAN A marar 20 dB dB to subtract from measurement to scale to pressure at 1 meter 20 log distance 12 dB 6 dB 0 dB Ee 0 1 m 0 25 m 0 5 m 1 meter Figure A 1 shows a plot illustrating the correction factor in dB that should be subtracted from SPL measurements taken at distances less than 1 meter to scale them to the eguivalent SPL that DOC 100 Rev 1 2 Copyright 2013 Florida Research Instruments Inc would be obtained at 1 meter Some commonly used measurement distances are indicated To obtain the correction factor for any distance less than one meter simply take the logarithm of the distance and m
11. ultiply by 20 Subtract this value from the SPL you measured and this will give you the equivalent SPL at 1 meter It is convention to express SPL measurements at a distance of 1 meter However always be sure to state the distance used in your measurements when publishing papers This will aid other readers in interpreting your data and represents good scientific practice Example Setting up to make measurements that reflect expected pressure levels at one meter 1 Determine the distance from the sound source to the microphone e g 0 25 meters 2 If possible set the A to D converter gain such that the largest expected analog signal provides a digital output slightly smaller than the maximum converter output count 3 If possible adjust the scaling factor of the display software such that the peak value of a 1 volt 50 kHz sine wave input produces a reading of 94 dB 20 log distance which for a distance of 0 25 m yields 94 dB 20 log 0 25 m 94 dB 12 dB 82 dB The above scaling may be accomplished by either using the known gain factor for the A to D converter and the display software or by applying a 1 volt peak 0 707 V rms 50 kHz signal to the converter input using a signal generator The test generator output level may be determined either by direct measurement or if the generator provides a calibrated output by using the set value directly If it is not possible to scale your A to D recording hardware and software you wi
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