Pistonphone - an overview | ScienceDirect Topics (2023)

Full pistonphone kits are supplied with a barometer to allow compensation for atmospheric pressure.

From: Vehicle Refinement, 2004

Related terms:

  • Energy Engineering
  • Semiconductor
  • Amplifier
  • Amplitudes
  • Photons
  • Electric Potential
  • Measurer
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Test and Measurement Microphones

Dr.John Carey, in Sensor Technology Handbook, 2005

Pistonphone Calibrator

A pistonphone is a mechanical device in which a vibrating piston generates an acoustic pressure field within a cavity at a particular frequency, typically 250 Hz, having a fixed sound pressure level, typically 124 dB. When a microphone is partially inserted into an opening in this cavity, its diaphragm will be exposed to this same sound pressure level. The acoustic output level generated by a pistonphone is a function of the barometric pressure, so the value is specified for measurements made at sea level. When using a pistonphone, it therefore necessary to measure the barometric pressure at the measurement location and correct the specified output level of the pistonphone to compensate for the effect of atmospheric pressure variations from the sea level value.

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Noise Measurement

J. Kuehn, in Instrumentation Reference Book (Fourth Edition), 2010

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32.6.2 Field Calibration

This normally implies the use of a calibrated, traceable microphone calibrator (for example, a pistonphone) which will provide a stable, accurately known sound pressure, at a known frequency, to a microphone used in the field instrument set-up (for example, a sound-level meter).

Although such “calibration” is only a calibration at one point in frequency domain and at one level, it is an excellent check, required by most measurement standards. Its virtue is in showing departures from normal operation, signifying the need for maintenance and recalibration of instrumentation.

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Acoustical Measurement

Allan J. Zuckerwar, in Encyclopedia of Physical Science and Technology (Third Edition), 2003

I.A.7 Microphone Calibration

The three most widely used techniques for microphone calibration are the electrostatic actuator, the pistonphone, and the reciprocity procedure.

The electrostatic actuator is a flat metallic electrode positioned at a nominal distance d1 from the microphone membrane. A voltage applied between the electrode and membrane produces a uniform electrostatic pressure on the membrane. If an ac voltage υa is superimposed upon a high dc polarization voltage Va, then the applied ac voltage and resulting electrostatic pressure have the same frequency. The membrane responds to the electrostatic pressure as it would to a sound pressure. The electrode is slotted to relieve acoustic loading between the electrode and membrane. The electrostatic pressure exciting the membrane is


With typical values Va=800V, υa=30V rms, and d1=0.0005m, the rms pressure is 0.85Pa, or 93 dB. The technique is excellent for obtaining frequency response but is not suitable for absolute calibration because of a twofold uncertainty in the distance d1. First, the slots in the electrode necessitate a theoretically derived correction and, second, the polarization voltage shifts the equilibrium position of the membrane toward the actuator electrode.

The essential parts of a pistonphone are a coupler, into which the microphone cartridge is inserted and sealed, usually with an O-ring, and a vibrating piston of known displacement. The piston may be driven by a cam having a sinusoidal contour, generating a pure tone, or by a crankshaft, which in addition produces considerable second-harmonic distortion. The frequency is controlled through the speed of the cam or crankshaft. The pressure generated in the coupler is


where Sp is the piston area, d the rms stroke, and V the volume of the coupler (including the equivalent volume of the microphone). With typical values of γ=1.4, P0=105N/m2 (1atm), Sp=10−5m3, d=1.4×10−4m, and V=2×10−5m3, the rms pressure is 9.8Pa, or 114dB. At audio frequencies, a precision of a couple of tenths of a decibel is attainable. At low frequencies a correction is needed for nonadiabatic compression. In the form of a portable, battery-operated device, it is ideally suited for quick calibration of microphones in the field. Two limitations are fixed amplitude and relatively low operating frequency (several hundred hertz maximum). Devices using moving-coil drivers (without servo control) are not true pistonphones, for the generated volume velocity depends on the acoustic impedance of the load.

The reciprocity procedure is based on the following electromechanical principle. When a reversible transducer is operated as a receiver, the ratio of open-circuit output voltage υ to applied acoustic pressure p will equal some constant A. Then, when it is operated as a transmitter, the ratio of the generated volume velocity U to the input current I will equal the same constant A, if the acoustic load Zr is small (see Fig. 2a.a, b). According to this procedure, three transducers are placed pairwise in an acoustic coupler—a transmitter T, a reversible transducer R, and the test microphone M. In test 1, transmitter T generates a sound pressure PT to excite receiver R, resulting in an open-circuit voltage υR=ARPT. In test 2, test microphone M replaces transducer R to yield υM=AMPT. These lead to the relationship:


In test 3, transducer R, as transmitter, excites test microphone M, resulting in υ′M=AMPR. However, the above-stated reciprocity property, UR=ARIR, and the known acoustic impedance of the coupler, ZC=PR/UR, lead to the relationship:

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Substitution of Eq. (17) into (16) yields:


Thus, the microphone sensitivity depends only on electrical quantities, which are measurable to high precision, and a readily determinable acoustic impedance. The reciprocity method, the most precise of all known methods, can achieve absolute precisions of the order of hundredths of a decibel. A free-field variation of the procedure is similar but is beset with practical difficulties.

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Introduction of self-sustained thermoacoustic instability

Dan Zhao, in Thermoacoustic Combustion Instability Control, 2023

1.6.3 Experimental studies

Experimental studies are conducted on a well-designed T-shaped combustion system to measure the growth rate Gα/ω of combustion-driven oscillations normalized by its frequency. This test rig is a spin-off of classical Rijke-type combustor [18,19]. The schematic of the experimental setup is shown in Fig. 1.29. The bottom stem of the T-combustor is 30cm long and has an inner diameter of 50mm. The bifurcating branches sharing the same inner diameter of 45mm and the same axial length of 50cm. A perforated pipe made of acrylic materials is attached to the T-shaped combustor. To protect the perforated pipe with an axial length of 15cm and inner diameter of 45mm, a centrifugal pump is implemented. It pumps ambient air through the perforated pipe joining the combustion flow and flowing out through the right-hand-side horizontal branch of the T-combustor. The cooling flow rate is in the range of 0–0.1074m3/s. The perforated pipe involves with 112 circle-shaped orifices with a diameter of 3mm. these orifices are distributed equally in space along the pipe surface. Acoustic pressure measurements are conducted by using 2 arrays of B& K 4957 microphones with a sensitivity of 11.2mV/Pa. The microphones are calibrated with B&K Pistonphone (124dB @250Hz, Type 4228). A premixed conical-shaped flame is confined at 13.5cm away from the bottom open inlet.

Pistonphone - an overview | ScienceDirect Topics (1)

Figure 1.29. Schematics of the experimental rig of T-shaped combustion system with a cooling perforated pipe applied.

Adapted from Zhao D. Thermodynamics-acoustics coupling studies on self-excited combustion oscillations maximum growth rate. J Ther Sci 2020. https://doi.org/10.1007/s11630-020-1361-8.

The measured combustion-driven oscillations from the 4 pressure sensors are shown in Fig. 1.30. It shows the time evolution of the phase diagram/plot between the pressure p′(t) (Pa) and its gradient dp′(t)/dt (Pa/s). The combustion-driven oscillations are limit cycles initially at t≤20s, as revealed by the circle-shaped phase plot. This is known as Rijke-type thermoacoustic phenomena as discussed by Feldman JR [18]. However, as the cooling flow rate is increased to 5.5m/s, the oscillations are attenuated (see 30s≤t≤60s). At t=60s, the cooling flow rate is suddenly reduced to 0m/s. The combustion-driven oscillations quickly grow into limit cycles.

Pistonphone - an overview | ScienceDirect Topics (2)

Figure 1.30. Experimentally measured combustion-driven pulsating oscillations from the acoustic sensor 1 (A), sensor 2 (B), sensor 3 (C), and sensor 4 (D).

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Adapted from Zhao D. Thermodynamics-acoustics coupling studies on self-excited combustion oscillations maximum growth rate. J Ther Sci 2020. https://doi.org/10.1007/s11630-020-1361-8.

Time evolution of the local peaks/amplitude of the experimentally measured acoustic pressure fluctuations [18,19] is shown in Fig. 1.31. Fig. 1.31A and B illustrates the two sensors measurements on left- and right-hand-side bifurcating branches respectively. The growth rate α is determined by fitting the linear equation (denoted by the dash line). The frequency of the measured acoustic fluctuations is shown in Fig. 1.31C in the pressure spectrum. It is approximately 215Hz. There are harmonic peaks in the spectrum. However, these peaks magnitudes are at least 1 order lower than the dominant peak at 215Hz. With the dominant oscillation frequency determined, the mode-shape as experimentally measured is shown in Fig. 1.31D. The combustion system is a standing-wave one [87,136]. This confirms that the acoustic frequency is intrinsically selected according to the longitudinal resonance nature of the combustor. In practice, such self-sustained limit cycle oscillations [144,157–176] are desirable in thermoacoustic Stirling engines [144] and refridges [148].

Pistonphone - an overview | ScienceDirect Topics (3)

Figure 1.31. Experimentally measured growth rate α of the dominant pulsating oscillation from sensor 1: α=1.676 and β=−100.16 (A); sensor 2 α=1.603 and β=−95.38 (B), sensor 3: α=1.668 and β=−99.24 (C) and sensor 4: α=1.669 and β=−99.09 (D). The measured dominant frequency is 215Hz. The normalized growth rate Gexp≡(α/ω)exp. is (A) 1.24×10−3, (B) 1.18×10−3, (C) 1.23×10−3 and (D) ×10−3.

Adapted from Zhao D. Thermodynamics-acoustics coupling studies on self-excited combustion oscillations maximum growth rate. J Ther Sci 2020. https://doi.org/10.1007/s11630-020-1361-8.

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Aeroacoustic testing and instrumentation

Stewart Glegg, William Devenport, in Aeroacoustics of Low Mach Number Flows, 2017

10.3 Sound measurement

Sound measurements at conditions likely to be generated by low Mach number flows are commonly made using condenser microphones—microphones that use the change in capacitance between a membrane and a backing plate. The membrane vibrates in response to the sound, and the capacitance changes as the distance between the membrane and the backing plate fluctuates as a function of time. Conventional condenser microphones require a power source to maintain a charge across the membrane and the backing plate, so a change in capacitance appears as a change in voltage. In electret microphones either the diaphragm or the fixed plate of the capacitor is made from a ferro-electric material that carries a permanent electric charge (referred to as prepolarized). This eliminates the need for a voltage source for the microphone, though power is usually still required because an integrated preamplifier is commonly part of these devices.

Instrumentation microphones designed for scientific work are often the most expensive but can provide well-defined, accurately documented, and stable characteristics. Examples are the 1/2-in. diameter B&K 4190 illustrated in Fig. 10.26A and the 1/4-in. G.R.A.S. 40-PH-S5-1 shown in Fig. 10.26B. Microphones of this type may be provided with documentation of their frequency response when exposed to plane sound waves parallel to the diaphragm, as well as deviations from that response for off-axis sound (e.g., Fig. 10.27). Within its operating range (6.3Hz–20kHz for the B&K 4190) this type of microphone will generally have an almost constant amplitude response to sources ahead of the diaphragm so that in this range only a single value of the microphone sensitivity is needed to make a quantitative sound measurement. Precise measurement of this sensitivity (to account for environmental conditions at the time of a measurement) can be made using a pistonphone. This is a handheld device produces pressure fluctuations of known amplitude by using the mechanical motion of a vibrating piston at a fixed frequency to simulate a sound wave by compressing a fixed volume of air to which the microphone diaphragm is exposed.

Pistonphone - an overview | ScienceDirect Topics (4)

Fig. 10.26. Examples of microphones for sound measurement. All are shown on the same scale, which may be inferred from the 1/2-in. diameter microphone in part (A) B&K model 4190, (B) G.R.A.S. 40-PH-S5-1, (C) B&K model 4138, (D) Sennheiser KE 4-211-2, and (E) Panasonic WM-64PNT.

Pistonphone - an overview | ScienceDirect Topics (5)

Fig. 10.27. Amplitude response as a function of frequency and direction for a B&K 4190 1/2-in. microphone with (a) standard protection grid and (b) B&K model UA 0386 nose cone (curves for 0 and 180 degrees coincident).

Data provided by Brűel and Kjaer.

Instrumentation microphones come in a range of diameters. Large diameter microphones (e.g., 1/2 or 1in.) are more sensitive to acoustic pressure fluctuations because those fluctuations are integrated over a larger diaphragm area. Such microphones are useful for measuring sources that are particularly quiet at laboratory scale, such as roughness noise, where good electrical signal-to-noise ratio is needed. At the same time, the larger diaphragm has greater inertia limiting the frequency response. While suffering from lower sensitivity, smaller diameter microphones (e.g., 1/4 and 1/8in.) may have a greater range, both in terms of the intensity of the sound and the frequencies they can measure. For example, the B&K model 4138 1/8in. microphone pictured in Fig. 10.26C can measure sounds up to 168dB and 140kHz.

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The size of the diaphragm is also important compared to the wavelength of the sound. When the wavelength becomes comparable to the diameter then the scattering of the sound field around the end of the microphone and the spatial distribution of the diaphragm sensitivity become important in determining the response. Fig. 10.27 shows, for example, the deviations in the response of the B&K 4190 with the direction of the incident sound. This microphone has a 1/2-in. diaphragm, and we see that the directionality of the sound becomes a substantial factor at around 6kHz, where the quarter wavelength is approximately equal to the diaphragm diameter. At 20kHz, the microphone is 10dB less sensitive to sound directed at the side of the microphone, or from behind, than it is to sound originating from in front. Instrumentation microphones are usually designated as free-field microphones (like the B&K model 4190), optimized as far as possible to measure sound incident on the microphone from any direction, or pressure-field microphones designed to measure sound (or fluid dynamic pressure fluctuations) at a wall. Pressure-field microphones, such as the B&K model 4138 in Fig. 10.26C, usually include a vent designed to equalize the mean pressure on the two sides of the microphone for situations where the face of the microphone is exposed to a pressure significantly different from ambient.

At the lower end of the cost spectrum are devices designed for mass market applications such as lavalier microphones, cell-phones, hearing aids, and units designed for the recording and performance industry. Many of these devices are electret microphones, and a subset can be used for sound measurement in low Mach number applications as long as the experimentalist is willing to take the time to select and calibrate these sensors to the precision needed for scientific work. It is common practice to perform frequency response calibrations of such microphones using an instrumentation microphone as a reference, by subjecting both microphones to a broadband sound field generated by a loud speaker. Such a calibration needs to be done in an environment with a well-defined acoustic character, such as a sealed cavity, a pipe, or an anechoic chamber. Consistent placement and configuration of the test and reference microphones is usually critical to ensure that they are exposed to exactly the same sound field. Examples of such microphones include the Sennheiser KE 4-211-2 shown in Fig. 10.26D and the Panasonic WM-64PNT of Fig. 10.26E. Stability, low noise, and adequate amplitude and frequency range are important considerations in selecting a low-cost microphone for an aeroacoustic test. For situations where multiple microphones are to be used as part of a system (such as a phased microphone array) measuring and matching the phase calibrations of the microphones are often crucial.

The placement and mounting of microphones outside of the test flow involves a number of considerations. It is usually desirable for the microphone to be as close as possible to the source to maximize signal-to-noise ratio. At the same time, keeping the microphone in the acoustic far field (at least one wavelength from the source) is often desirable to simplify the interpretation of the measurement. Also, placing the microphone too close to the free jet or acoustic window can result in contamination by near-field pressure fluctuations associated with the turbulent shear layer. It is usual to orient the microphone to point as directly as possible at the source. This aligns the wavefronts parallel to the diaphragm and makes use of the most favorable microphone response. To exploit the best characteristics of the anechoic chamber, microphones are usually placed at least a quarter wavelength away from the walls, defined by the wedge tips. To avoid unpredictable scattering effects microphones should either use slender mounts and be held from behind or be mounted on a solid surface designed to cleanly reflect the incoming acoustic waves (in which case the measured sound pressure amplitude is doubled because of the addition of the incident and reflected waves). Fig. 10.28 shows single microphones mounted with these considerations in mind in an open-jet wind tunnel. Note that acoustic foam is wrapped around the support beams of the microphone gantry in order to reduce acoustic reflections. Two different mounting strategies for a microphone array are shown in Figs. 10.29 and 10.30. In Fig. 10.29 the microphones are mounted flush in the face of a circular carbon fiber disk designed to reflect the sound, and in Fig. 10.30 the microphones are supported from behind using an open lattice designed to transmit the sound at wavelengths of interest.

Pistonphone - an overview | ScienceDirect Topics (6)

Fig. 10.28. Microphone mounting in an anechoic wall jet wind tunnel.

Pistonphone - an overview | ScienceDirect Topics (7)

Fig. 10.29. Microphones mounted in a carbon fiber disk to form a 117-microphone phased array.

Pistonphone - an overview | ScienceDirect Topics (8)

Fig. 10.30. Microphones mounted from behind using an open lattice in the anechoic chamber of a hybrid anechoic wind tunnel.

It is often of interest to obtain sound measurements at angles that require placing microphones inside the flow. A good example here is rotor testing, where sound radiated on or near the rotor axis is of particular scientific interest. When a microphone is placed directly in the flow its signal will be contaminated with turbulent and sound pressure fluctuations resulting from the interaction of the microphone and its support with the flow. To minimize the contamination an aerodynamic fore-body is used with the microphone, and a streamlined fairing is placed over the supporting strut. The typical microphone fairing shown in Fig. 10.31 is a 1/2-in. diameter B&K model UA 0386 nose cone. This consists of a bullet-shaped housing with a circumferential opening covered by a porous screen. When mounted to the front of a microphone the space interior to the screen forms a cylindrical cavity with one face formed by the microphone diaphragm. Regardless of the orientation of the acoustic source of interest, the microphone is mounted with the nose-cone facing directly into the flow. In this position its streamlined shape minimizes the generation of turbulence, and the screen keeps any flow generated pressure fluctuations separated from the diaphragm. Furthermore, the screen tends to average out turbulent pressure fluctuations that are incoherent around its circumference. The principal drawback of this arrangement is that the nose cone changes the response of the microphone to sound at wavelengths of comparable size. Fig. 10.27 shows the effect of this nose cone on the free-field response of the 1/2-in. B&K 4190 microphone. For sound waves directed roughly at the face of the microphone θ=0degrees and 30degrees the nose cone considerably attenuates the intensity of the sound measured at frequencies above about 15kHz. The forebody actually amplifies sound coming from the side and behind in this frequency range. Obviously, these effects need to be corrected if sound at these frequencies is to be measured accurately. Note that other longer forebody designs can further reduce flow noise contamination [15].

Pistonphone - an overview | ScienceDirect Topics (9)

Fig. 10.31. Microphone with nose cone mounted in the flow using a faired strut.

The design of the strut supporting the microphone in the flow is equally critical. Even as a streamlined airfoil, the strut will be an acoustic source that competes with the sound produced by the model under test. Making the strut as quiet as possible, maximizing the distance of the microphone from the strut (by using a long sting support) can be simple and effective measures. (Note that Fig. 10.31 shows a microphone being used to measure relatively intense sound from a rotor system, and thus a short microphone sting was adequate in this case.) Ideally, the airfoil section chosen for the strut needs to be quiet. In particular, it must not generate vortex shedding tones while being thick enough to provide rigid structural support for the microphone. The McMasters-Henderson airfoil [16], a symmetric 28% thick section illustrated in Fig. 10.32, works well in this role [15].

Pistonphone - an overview | ScienceDirect Topics (10)

Fig. 10.32. The McMasters Henderson airfoil section [16], with coordinates.

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What is a piston phone sound level calibrator? ›

Pistonphones and sound calibrators are instruments designed for sensitivity checking and calibration of measurement microphones. In order to do that, these instruments can produce a reference signal at a specific level and frequency.

What is pistonphone? ›

A pistonphone is an acoustical calibrator (sound source) that uses a closed coupling volume to generate a precise sound pressure for the calibration of measurement microphones.

How accurate are phone decibel readers? ›

The study showed sound level measurements to be within ±1 dB of the reference system using the same test setup and apps from the initial study.

How accurate is a sound level meter? ›

For compliance purposes, readings with an ANSI Type 2 sound level meter and dosimeter are considered to have an accuracy of ±2 dBA, while a Type 1 instrument has an accuracy of ±1 dBA.

How do you use a Pistonphone? ›

The operating procedure is straight forward, simply fit the microphone into the coupler of the Pistonphone and switch on. The Pistonphone will now produce a constant sound pressure level on the diaphragm of the microphone.

What frequency is a microphone calibration? ›

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.

What is the standard for calibration of a microphone? ›

The frequency range of calibration is usually 2.5 kHz to 20 kHz, although, on request, calibrations are performed at frequencies from about 1.25 kHz to greater than 50 kHz.

How many dB is a normal phone? ›

Audio devices and mobile phones including iPhone have a sound level of 100 dB or louder. iPhones can produce a maximum of 115 decibels (software limits European iPods to 100 dB; U.S. models have been measured higher), the equivalent of attending a rock concert amplification.

How many decibels is too loud? ›

Sound is measured in decibels (dB). A whisper is about 30 dB, normal conversation is about 60 dB, and a motorcycle engine running is about 95 dB. Noise above 70 dB over a prolonged period of time may start to damage your hearing. Loud noise above 120 dB can cause immediate harm to your ears.

What is a safe decibel level? ›

Because people can't hear all frequencies, or pitches of sound, A-weighted decibels (dBA) can be used to describe sound based on what human ears can actually hear. Sounds at or below 70 dBA are generally considered safe. Any sound at or above 85 dBA is more likely to damage your hearing over time.

Can I use my phone as a dB meter? ›

Decibel X. Turns your smartphone into a pre-calibrated, accurate and easily portable sound level meter. It has a standard measurement range from 30 to 130 dB, boasts many features for measuring the intensity of sound around you, all of which is built into a nicely-designed, intuitive user interface.

How loud is 80 decibels? ›

80 decibels is fairly loud. It's equivalent to the noise of a busy downtown street. Being loud, it is a noise level that may harm your hearing if you are exposed to it for longer periods (more than 8-10 hours/day).

How many decibels is a noticeable difference? ›

The threshold of perception of the human ear is approximately three decibels and a five-decibel change is considered to be clearly noticeable to the ear.

Is higher Hz better for microphone? ›

The golden rule: the higher the sample-frequency is, the better is the sound-quality (although I think only a trained ear may able to resolve the difference). On the other side, a higher sample-frequency will lead to bigger audio-files in the case you perform records.

What kHz is best for microphone? ›

For most music applications, 44.1 kHz is the best sample rate to go for. 48 kHz is common when creating music or other audio for video. Higher sample rates can have advantages for professional music and audio production work, but many professionals work at 44.1 kHz.

What is the standard mic sensitivity? ›

Microphone sensitivity is typically measured with a 1 kHz sine wave at a 94 dB sound pressure level (SPL), or 1 pascal (Pa) pressure. The magnitude of the analog or digital output signal from the microphone with that input stimulus is a measure of its sensitivity.

What should my mic input level be? ›

Speak into the microphone at the same volume and distance you will use when recording. While you are speaking, watch the Input Level for the microphone. The input level should reach about two-thirds of the way to the top. Take note if the volume needs to be raised or lowered.

What should I read to test my microphone? ›

  • The small pup gnawed a hole in the sock.
  • The fish twisted and turned on the bent hook.
  • Press the pants and sew a button on the vest.
  • The swan dive was far short of perfect.
  • The beauty of the view stunned the young boy.
  • Two blue fish swam in the tank.
  • Her purse was full of useless trash.

What frequency is mic distortion? ›

If the microphone is placed in a sound field of a pure tone (e.g. 1 kHz) the distortion products – the harmonics generated – include frequency components at 2 kHz, 3 kHz, 4 kHz, etc. normally decreasing in level. (In case of symmetrical clipping, just uneven harmonics are generated, 3rd, 5th, 7th, etc.).

What does a Sound Level Calibrator do? ›

A Sound Level Calibrator or Acoustic Calibrator is a hand-held device that emits an audible tone of very accurate level and frequency. Before making noise measurements the Calibrator is fitted over the meter's microphone and the reading is either checked manually by the user or automatically by the meter.

How do you use a sound calibrator? ›

Using a Sound Calibrator

All sound level meters have either an adjustment screw or some form of automatic calibration feature. Carefully place the calibrator over the microphone, ensuring it is a snug fit, and switch it on. Check that the display reads the level that will be specified in the manual.

What is a standard Sound Level Calibrator? ›

The sound calibrator usually provides a reference sound pressure level of 94 dB or/and 114 dB at the frequency of 1 kHz. The sound calibrator must have a traceable and documented calibration certificate from a higher level laboratory (often from a national metrology institute).

How often should a sound level meter be calibrated? ›

We recommend that equipment is returned for calibration once every year. This fits in with most calibration and service schedules and with many noise measurement regulations. Some regulations, such as those for UK and EU Noise at Work, state that the calibration should be carried out at least every two years.

What are acceptable sound levels? ›

The U.S. Environmental Protection Agency (EPA) and the World Health Organization (WHO) recommend maintaining environmental noises below 70 dBA over 24-hours (75 dBA over 8-hours) to prevent noise-induced hearing loss.

How often do you need to calibrate a noise meter? ›

You need to calibrate the equipment in laboratories: Once every 12 months. According to manufacturers' recommendations.

What is the difference between Type 1 and Type 2 sound level meter? ›

A Class 1 sound level meter is often called a 'precision' grade meter and a Class 2 sound level meter is a 'general grade' meter because of their difference tolerance levels. At lower and upper extremities of the sound frequency range* tolerances are wider, and at higher frequencies, the tolerances are narrower.

What is the best way to measure sound level? ›

The most common instrument used for measure noise levels is a Noise Level Meter (also known as a sound level meter). In its most basic form, a noise level meter consists of a microphone, internal electronic components, and a display.

How do you use Pistonphone? ›

The operating procedure is straight forward, simply fit the microphone into the coupler of the Pistonphone and switch on. The Pistonphone will now produce a constant sound pressure level on the diaphragm of the microphone.

What is the metric for sound quality? ›

Usually the higher the decibel (Db), the better the quality of sound. For instance, a signal-to-noise ratio of 90 or 100 decibels is considered high fidelity. Most electronics are usually 80 decibels or over which is great for many discerning human ears.

What scale is a sound level meter? ›

This scale is called the decibel scale or dB scale. On the decibel scale, 0 dB is the smallest audible sound. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB.

What is the ISO standard for sound measurement? ›

The ISO standard that showed most promise was the ISO 3744. This standard uses a method with fairly high accuracy and is quite easy to implement compared to other standards tested.


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