The Pistonphone is a precision sound source for calibrating microphones.
 

Calibration is an essential step in every precision measurement. It establishes the relationship between the sound pressure and the electrical output of the microphone.
 

Calibration can be performed at either 250 Hz or at 1 kHz. Both frequencies have their advantages and disadvantages.
 

250 Hz is in the frequency range where the frequency response of almost all microphones is flat and will therefore give the most accurate calibration.
 

If, however, the microphone is used in connection with measuring equipment with weighting filters, for example a sound level meter with A-weighting, the 250 Hz signal will be attenuated by the weighting network. In this case it might be advantageous to use a 1 kHz calibration frequency.
 

At 1 kHz, the weighting filters have 0 dB attenuation and will therefore not affect the calibration. On the other hand, since the frequency response of the microphone is not flat, a small error could be introduced.
 

Click on images for details:

Sound Calibration   : :   G.R.A.S. Sound & Vibration
	Type 42AB Sound Calibrator      Sound pressure level:           114 dB (re. 20 µPa) ± 0.2 dB   Frequency:           1,000 Hz   Temperature range:           -10 °C to +50 °C   Batteries:           6LR61, 9 V   Accuracy:           IEC 942 (1988) Class 1   Weight:           220 g   Comment:           Portable, battery operated           calibrator            Produces a constant sound           pressure level of 114 dB           re. 20µPa (equivalent to           10 Pa) at 1,000 Hz           Requires no corrections for           ambient pressure changes           or microphone equivalent           volume            Includes adapters for           calibrating 1", ½" and           ¼" microphones		Type 42AA Pistonphone    Sound pressure level:           114 dB (re. 20 µPa) ± 0.08 dB   Frequency:           250 Hz   Temperature range:           -10 °C to +55 °C   Batteries:           4 x AA alkaline (IEC LR 6)   Accuracy:           IEC 942 (1988) Class 1   Weight:           325 g   Comment:           Precision sound source for           calibrating microphones           Battery operated, produces           a constant sound pressure           level of 114 dB re. 20µPa           (equivalent to 10 Pa) at           250 Hz, or 105.4 dBA re.           20µPa            Each Type 42AA is within           0.1 dB of the nominal value           and is delivered with an           individual calibration chart           and a barometer for Class 1           static pressure corrections           For Class 0 static pressure           corrections, a precision           barometer is required		Type 42AC High Level Pistonphone    Sound pressure level:           134 dB (re. 20 µPa) ± 0.08   Frequency:           250 Hz   Temperature range:           -10 °C to +55 °C   Batteries:           4 x AA alkaline (IEC LR M6)   Accuracy:           IEC 942 (1988) Class 1   Weight:           325 g   Comment:           Precision sound source for           calibrating microphones           Battery operated, produces           a constant sound pressure           level of 134 dB re. 20µPa           (equivalent to 100 Pa) at           250 Hz, or 125.4 dBA re.           20µPa            Each Type 42AC is within           0.1 dB of the nominal value           and is delivered with an           individual calibration chart           and a barometer for Class 1           static pressure corrections           For Class 0 static pressure           corrections, a precision           barometer is required		Type 42AP Intelligent Pistonphone    Sound pressure level:           114 dB (re. 20 µPa) ± 0.05 dB   Frequency:           250 Hz and 251.2 Hz   Temperature range:           -10 °C to +55 °C   Batteries:           4 x AA alkaline (IEC LR 6)   External power:           6V DC 125mA   Accuracy:           IEC 60942 (ed.3/DIS) LS   Weight:           437 g   Comment:           Battery-operated, precision           sound source for accurate           and reliable calibration           Built-in precision barometer           and thermometer           Actual sound pressure level,           corrected for static ambient           pressure, is shown on display           Individual calibration chart           delivered with each           pistonphone            Display can be switched to           show any of the following:           * Actual corrected sound               pressure level in decibels           * Actual corrected sound               pressure level in decibels               if measured with an               A-weighting filter           * Static air pressure in hPa           * Calibration temp. in °C           * Calibration temp in in °F           Extremely stable laboratory           standard sound source which           can also be used for field           calibrations - it retains its           high accuracy even under           hostile environmental           conditions            Remote control available via           RS-232 connection
	Type 42AE Low Frequency Calibrator    Comment:           Permits microphone           calibration at frequencies           down to 0.01 Hz for both           front and rear-vented           microphones            Produces a constant sound           pressure level down to very           low frequencies           Two-port configuration allows           the actual sound pressure in           the coupler to be monitored           by a reference microphone           simultaneously with the           microphone under test           Built-in DC-coupled power           amplifier enables the           calibration to be used for           swept-sine, broadband and           step function investigations           Accepts all microphone sizes           from 1/8", ¼", ½" and 1"           front and rear-vented           microphones            Frequency range from           0.27 Hz - 100 Hz           Calibration levels up to           140 dB (re. 20 µPa)		Type 90CA Microphone Calibration System    Comment:           Calibration of all types of           IEC 61094 standardized           ¼", ½" and 1" measurement           microphones            Automated and reliable level           and frequency response           calibration            Microphone Calibration in           Four Easy Steps:           1. Microphone Registration           2. Level Calibration           3. Frequency Calibration           4. Print Calibration Certificate           Main Features:           * Ready-to-use software               and hardware           * Accurate calibration               hardware           * Automated and computer-               controlled calibration               process           * Highly reproducible               calibration method           * Pre-installed test               parameters for G.R.A.S.               microphones           * Test conditions easily               changeable           * customisable documents               and certificates for printing               and archiving		AL0010  Calibration Stand    Comment:           Convenient platform for           testing condenser           microphones            It has a fixture for holding           a ½" preamplifier (e.g. Type           26AK) securely in place as           well as recesses and a           column for safely parking           electro-static actuators           (i.e. RA0014 and RA0015)           and microphone protection           grids when not in use           It can be set-up for both           ½" and 1" microphones           The AL0010 is a useful           addition to a set up (which           includes a Type 14AA) for           routinely calibrating           condenser microphones.

Electrostatic Actuators   : :   G.R.A.S. Sound & Vibration
	RA0014  ½" Electrostatic Actuator   Comment:           For testing the frequency           response of standard ½" and           ¼" microphones           Adapter included for testing           ¼" microphones           Can be connected directly to           the Actuator Supply           Type 14AA		RA0015  1" Electrostatic Actuator   Comment:           For testing the frequency           response of standard 1"           microphones            Can be connected directly to           the Actuator Supply           Type 14AA		Type 14AA Actuator Power Supply   Input Signal:           3 V peak-to-peak    Gain:           +40 dB    Output Signal:           300 V peak-to-peak    Actuator Polarisation Voltage:           800 V    Frequency response:           1 Hz - 200 kHz    Output impedance:           1 k Ohm    Power supply:           110 /130 V AC or           220/240 V AC    Weight:           1.4 kg    Comment:           High-voltage, high-gain           amplifier and voltage supply           for driving electrostatic           actuators            The high-voltage output can           also be used to drive standard           microphones as sound           sources            The Type 14AA can drive an           electrostatic actuator with a           300 V peak-to-peak signal           superimposed on 800 V DC            Its wide frequency range           makes it possible to           determine the pressure           frequency response of           condenser microphones from           200 Hz to 200 kHz            The Type 14AA together with           RA0014 and RA0015           electrostatic actuators comply           with IEC 61094 - 6           "Measurement microphones -           Part 6: Electrostatic actuators           for determination of frequency           responses"

 
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Other G.R.A.S. Sound and Vibration products

• Easy selection Microphone Sets 
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  • KEMAR Head & Torso Simulator
  • ANSI/ASA S12.42 test fixture
  • Telephone Test Head
  • Hearing-protector Test Fixture
• Pistonphones and Calibration equipment  
• Intensity microphones and calibrators
• Intensity Probes
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