Decibel (dB) The word decibel is used in different contexts, for example to describe sound pressure and hearing loss. The abbreviation for decibel is dB.

Decibel is a relative unit of measure. Therefore, when used alone, dB indicates how loud a given sound is relative to another. This could for example be the amount of amplification delivered by a hearing aid. As the term decibel is used in many contexts, it is often necessary to specify the type of decibel referred to by attaching an abbreviation to it. For example:

dB SPL means dB Sound Pressure Level and indicates the sound pres-sure relative to the weakest sound which an individual with normal hearing can hear. This means that 0 dB SPL is the weakest sound that a person with normal hearing can detect.

dB HL means dB Hearing Level and indicates a person’s hearing relative to accepted standards for normal hear-ing. So, 40 dB HL means that the per-son has a hearing loss of 40 dB. dB HL is the unit used in an audiogram.

Decibel scale

Sound is produced when the mole-cules in the air are caused to vibrate. Sound intensity is an indication of the magnitude of these vibrations. A 6 dB increase of the sound intensity cor-responds to the doubling of the inten-sity. This means that a sound intensity of 106 dB is physically speaking twice as powerful as one of 100 dB.

That is the reason for using a log-arithmic scale instead of, for example, an ordinary linear scale. When using a logarithmic scale, it doesn’t make sense to talk about “percentage of hearing loss”. dB HL refers to the hearing loss at a specific frequency in relation to normal hearing.

See also:

Audiogram

Frequency

Sound