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The threshold of hearing is generally reported in reference to the RMS sound pressure of 20 micropascals, i.e. 0 dB SPL, corresponding to a sound intensity of 0.98 pW/m 2 at 1 atmosphere and 25 °C. [3]
The levels are weighted with frequency relative to a standard graph known as the minimum audibility curve, which is intended to represent "normal" hearing. The threshold of hearing is set at around 0 phon on the equal-loudness contours (i.e. 20 micropascals, approximately the quietest sound a young healthy human can detect), [15] but is ...
For humans, normal hearing is between −10 dB(HL) and 15 dB(HL), [2] [3] although 0 dB from 250 Hz to 8 kHz is deemed to be 'average' normal hearing. Hearing thresholds of humans and other mammals can be found with behavioural hearing tests or physiological tests used in audiometry.
which is often considered as the threshold of human hearing (roughly the sound of a mosquito flying 3 m away). The proper notations for sound pressure level using this reference are L p/(20 μPa) or L p (re 20 μPa), but the suffix notations dB SPL, dB(SPL), dBSPL, or dB SPL are very common, even if they are not accepted by the SI. [8]
Pure-tone audiometry is the main hearing test used to identify hearing threshold levels of an individual, enabling determination of the degree, type and configuration of a hearing loss [1] [2] and thus providing a basis for diagnosis and management.
Probably the most common usage of "decibels" in reference to sound level is dB SPL, sound pressure level referenced to the nominal threshold of human hearing: [49] The measures of pressure (a root-power quantity) use the factor of 20, and the measures of power (e.g. dB SIL and dB SWL) use the factor of 10.
A tone at the frequency of 4000 Hz is presented for 60 seconds at an intensity of 5 decibels above the patient's absolute threshold of hearing. If the patient stops hearing the tone before 60 seconds, the intensity level is increased by another 5 decibels with the procedure repeated until the tone can be heard for the full 60 seconds or until no decibel level can be found where the tone can be ...
Hearing level is the sound pressure level produced by an audiometer at a specific frequency. It is measured in decibels with reference to audiometric zero. [ 1 ] Hearing of speech is considered to be impaired when the hearing level is shifted 25 dB or more.