Can You Hear Me Now?

The difference between loudness, sound quality and audibility is interesting. During the dark ages of acoustics, much attention was given to measurements of dB or how loud the sound was. Ordinances were written to limit the dB level at a property line and as long as the measured sound was below the noted dB level, the problem was solved.

Some years ago, equipment manufacturers discovered that if the product had a “pleasant” sound, as described by a focus group”, the product would gain better acceptance in the marketplace. The manufacturers changed the acoustics of the equipment with materials to absorb or mitigate particular frequencies that buyers often found annoying. Particular attention was paid to any mechanical equipment as the low frequency noise was often objectionable. For example, automobile manufacturers discovered buyers believed the car was more durable and of better quality with certain tones from the engine and doors. Therefore, the new parameters of sound included both loudness and sound quality.

More recently, as urban and suburban areas became denser, audibility gained significance. For example, apartments near an office building may be annoyed by the rooftop chiller. When the loudness is measured, the dB level may be very close to the background noise level when the chiller is not in operation. The audibility, however, is discernible as the mechanical parts produce low frequency tones that are clearly heard. Some noise ordinances now, the Department of Environmental Protection for example, measure not only the dB level but any “pure tones” that are produced by the noise source. A pure tone is a frequency that is significantly louder than the adjacent frequencies and, therefore, is very audible.

If you manufacture equipment or have a complaining neighbor, NEVA can assist you in determining how restore the quiet by changing the loudness, sound quality and audibility.