Category: (((—Acoustics Engineering—))))

The piezoelectric accelerometer is a seismic mass type of accelerometer that works on the principle described above. The main types include the following: compression, delta shear, planar shear, theta shear, annular shear, and ortho shear. These are all designed to accentuate certain advantages that are useful in different environmental conditions and are described in more…

Modern‐day piezoelectric accelerometers and some of the earlier displacement transducers [23] work on the same principle: A seismic mass m is supported on a spring of stiffness k and the whole is enclosed in a case (see Figure 7.13). The damping constant R in most applications is small, and it is neglected for simplicity in the following analysis (although it could easily…

A vibration sensor is a device that converts some property of the vibration of a structure into an electrical signal. Conversely, a vibration generator works on the opposite principle of converting an electrical signal into a mechanical vibration. Both vibration sensors and generators may be termed transducers, since they convert one physical variable into another…

When two phase‐matched microphones are used together to form a sound intensity probe, then the two‐microphone intensity probe can be calibrated by fitting an intensity coupler attached to the pistonphone [7]. The coupler normally consists of two chambers (upper and lower) connected by a coupling element. When the pistonphone is connected to the coupler, a…

Somewhat simpler, lower cost calibrators are also available that work on the driven‐diaphragm principle. Some commercially available types produce 114 dB at 1000 Hz. A stabilized 1000‐Hz oscillator feeds a piezoelectric driven element that vibrates the metallic diaphragm creating a pressure in the front coupling. The diaphragm is driven by an oscillator powered by a 9‐V battery.…

The pistonphone is a very accurate, reliable, and simple device for calibrating a microphone that is convenient for use in the field. The principle of operation is quite simple. A small battery‐powered electric motor drives a shaft on which is mounted a cam disk. The cam disk drives two pistons symmetrically. The cam gives the…

It is important to calibrate transducers used for sound, shock, and vibration to ensure the accuracy of measurements made with them. Proper calibration also ensures that the results measured with the transducers are comparable with the results measured by others. The accuracy of the calibration must also be known. The transducer system and the calibration method…

At low frequencies, for example, below about 1000 Hz, the frequency response of a microphone is independent of the angle of incidence of the sound waves. However, at higher frequencies, as the microphone dimensions and the wavelength of the sound become comparable, diffraction effects become important and the frequency response of a microphone is strongly dependent on the…

Since the human hearing range extends from about 20 to 20 000 Hz, it is desirable that the frequency response of microphones and noise measurement systems should be “flat” between these limits as shown in Figure 7.6. For certain types of measurements (e.g. for measurement of sonic booms or explosive blasts), it may be necessary to measure sounds that…

The magnitude of the frequency response, R(f), of an ideal microphone is given by Eq. (7.2a) as the frequency of the sound pressure p is changed. The magnitude of the frequency response, R(f), or an ideal accelerometer is given by Eq. (7.2b) as the frequency of the vibration a is changed. Figure 7.6 shows the frequency response of an ideal microphone used for noise measurements or an ideal accelerometer used…