Acoustic Measurements

measurements of the values that describe sounds and noises in terms of their intensities and various qualitative features (such as their spectra or the growth and decay of the sound over time). The principal values measured in acoustics are sound pressure, sound intensity, vibration velocity and particle displacement, the frequency and period of vibrations, propagation velocity, damping factor, and others. The most important characteristic is sound pressure, because the human ear responds to the sound wave pressure.

Acoustic measurements are closely linked with electrical measurements and are performed chiefly with electronic measuring instruments. The difficulties experienced in acoustic measurements are due to the complicated spatial distribution of the acoustic values in rooms as well as the variability of sounds and noises over time.

For sound pressure measurements a standard microphone is used in air or a hydrophone in water. The receiving portion of these instruments transforms the received acoustic signals (pressures) into proportional electric voltages, which are then fed to the input of amplifiers with indicators for readout. A sound-level meter is used for measuring various noises.

An important part of acoustic measurements is building and architectural acoustics—the measurements of the sound isolation of partitions and coverings and of the sound absorption factor of different structural coverings (such as plaster, upholstery, and floors).

There are other kinds of acoustic measurements such as measurements of waveguide characteristics, tests of acoustic instruments for communication and broadcasting (that is, of acoustic transmitters and receivers), tests of tape recorders and record players, and of telephone communication. Of special importance is the category of subjective measurements of the hearing sensitivity of people and its deviations from the norm (audiometry).