Absolute threshold of hearing

The threshold of hearing (also resting threshold ) is that the sound pressure or sound pressure level at which the human ear sounds or noises just perceives.

The hearing threshold is the lower limit of the listening area ( also referred to as acoustic field or listening ) - the upper limit is referred to as acoustic pain threshold.

Values

The hearing threshold is dependent on the frequency.

• At 2 kHz it is at a sound pressure level of zero decibels ( dB) equal to 20 uPA.
• Both at low frequencies and at very high levels, the hearing threshold is shifted to higher. Thus, both a deep sine wave of 30 Hz and a high of 15 kHz can be perceived by normal hearing only from a sound pressure level of about 60 dB.
• The most sensitive human hearing frequencies 3500-4000 Hz is in this frequency range it accepts sound pressure levels of up to minus 5 dB to register what ( 11,25 uPA ) corresponds to a sound pressure of only 1.125 · 10-5 Pascal.

• For the threshold of audibility of a sine tone of 1000 Hz, a sound pressure of 2.10 -5 was Pascal (20 uPA ) set as a reference value for the absolute sound pressure level ( an average value from measurements on many individuals ). Later it turned out that this value was set a little too low for 1000 Hz and about 2000 Hz applies to. Nevertheless, it was held at the original value.

The highest frequency that can be perceived is dependent on the age and health status. With age, the hearing threshold rises, especially at higher frequencies ( presbycusis ).

Measurement

The determination of the auditory threshold is performed with pure tones in the tone audiometry with sine waves of fixed frequency (usually 250, 500, 1000, 2000, 3000, 4000, 6000 and 8000 Hz).

When Békésy tracking the sound frequency changes slowly and continuously over the entire frequency range. The tones are presented on well calibrated headphones; alternatively, it can be determined with a frontally positioned sound source binaural hearing threshold.

The determination of the hearing threshold can be done with the so-called bracketing method or the method with increasing levels. When bracketing method, the hearing threshold is determined by averaging the results of measurements with increasing and decreasing level, the process with increasing levels of Prüftonpegel from the inaudible range is increased up to Audible becoming. In general, the methods of the rising level applies.

As a basis for the evaluation of hearing loss is the hearing threshold for normal hearing, as specified in DIN 45630 sheet about 2 and ISO 226:2003 as part of the " normal curves of the same volume level ." If hearing impaired, then deviates from the individual hearing threshold of the normal curve. The audiogram is the basis for the diagnosis of hearing damage.