refinement of the noise criteria rating system. The rating is determined by the speech interference level, resulting in the following classifications R is for Rumble, if the spectrum is rich in low frequency sound. H is for Hiss, if the spectrum is rich in high frequency sound. RV is for Rattle and Vibration, if the low frequency spectra is likely to produce audible rattling in lightweight building elements.
unit of atmospheric pressure, equal to 1000 millibars, one million dynes per square centimetre, 100 kilopascal or 29.53 inches of mercury.
the human ear combines sounds of similar frequency into frequency bands, called critical bands. Dr Zwicker divided the audio spectrum into 24 critical bands and named the units 'barks'. See also loudness.
IEC 801-23-14, phenomenon that results from the linear or non-linear superposition of two or more waves of the same kind but of different frequencies.
if two sound or vibration components are quite close together in frequency and are present at the same time at the same place, they will combine in such a way that their sum will vary in level at a rate equal to the difference in frequency between the two components. This phenomenon is known as beating and its frequency is the beat frequency.
a bel is equal to 10 decibels (dB) and because it is a ratio of two quantities it is dimensionless.
The decibel (dB) is used extensively to 'describe' acoustic levels.
sound recorded using two microphones spaced to simulate the listeners ears and usually transmitted separately to each ear of the listener. The results, using good quality headphones, can be very realistic.
multispectral measurements for correlation functions are performed using spectrum averaging. Half of the normal time record is set to zero. Accordingly, correlation functions for continuous signals will decrease with the delay. The bow-tie correction compensates for this.
also called wideband noise is noise whose energy is distributed over a wide section of the audible range as opposed to narrowband noise.