The audiogram records the softest level of sound a person detects at each frequency, based on specific test criteria. These detectable amounts of sound are referred to as the person’s hearing thresholds. During a hearing test, the audiologist will often attempt to obtain thresholds for many different frequencies in each ear, often using different methods (air conduction and bone conduction) to deliver the sound to the ear.
Look at the blank audiogram graph below. Along the top of the graph the numbers range between 125 to 8000. These numbers make reference to frequencies, or different pitches of sounds.
The frequency of any sound means the frequency of vibration of the sound source. The faster the rate of vibration, the higher the frequency in the sound. Sound frequency is generally measured in Hertz (Hz). A 250 Hertz (250Hz) tone looks like an in-depth, low-pitched horn. A tiny, tinkling bell has a high-pitch sound, probably measuring around 3,000 to 4,000 Hz.
Normal, healthy, young human ears can hear frequencies as little as 20Hz and up to 20,000Hz. However, audiologists test hearing within the range 250Hz to 8000Hz because the majority of the sounds of speech happen in this frequency range.
The intensity (loudness) of the sound is measured in decibels (dB). The decibel scale is shown on the side from the เครื่องช่วยฟังดิจิตอล. Audiologists want to use a number of different decibel scales, for the way the sound is measured. For hearing tests, sound is normally measured in decibels of Hearing Level (dB HL). This decibel scale reflects the sensitivity of the normally-hearing human ear.
The softest sounds that young people with normal hearing can detect in ideal listening conditions, is between zero and 20 ( – 20) dB HL, over the frequency range.
Conversational speech measured from one metre away is about 50 dB HL, though a few of the speech sounds will likely be around 35 to 40 dB HL.
Conversational speech measured from four metres away is going to be quieter, about 35 dB HL, with the softer speech sounds only measuring around 20 dB HL.
Really loud rock concerts can measure 110 to 120 dB HL. Lots of people find sounds over 100 dB HL unpleasantly loud. The incidence of hearing problems increases while we grow older. Over half the population aged between 60 and 70 have a hearing problems. This increases to more than 70 % of these older than 70, and 80 per cent of the over 80.
Hearing loss among veterans
War veterans will probably have problems with hearing problems because of damage from noise exposure in their service. Hearing is the second most typical medical problem reported by Australian war veterans and war widows, with 55 per cent reporting hearing difficulties being a current medical condition.
What is masking?
In a hearing test, sound being delivered to one ear can occasionally be heard by the opposite ear. This is usually only an issue if you have a change in hearing levels in between the two ears. Masking involves fpmaic a unique noise into one ear while testing the other ear. Audiologists use masking to learn which ear (cochlea) is hearing the test sound.
Sound heard in a room reaches both ears at very similar levels. When very small children are tested with sounds played out of a loudspeaker, the sound is assumed to become heard from the “better ear”, regardless of which ear is nearest the loudspeaker.
Sound delivered by headphones or insert earphones is less probably be cross-heard. Masking is usually only needed if there is a big difference in hearing levels in between the ears. Sound delivered by a bone conductor is readily cross-heard from the opposite ear. Masking is often required for bone conduction testing.