The audiogram records the softest level of sound an individual detects at each frequency, in accordance with specific test criteria. These detectable levels of sound are called the person’s hearing thresholds. In a hearing test, the audiologist will usually make an effort to obtain thresholds for a number of different frequencies in each ear, often using different methods (air conduction and bone conduction) to provide the sound to the ear.
Look at the blank audiogram graph below. Along the top of the the graph the numbers range between 125 to 8000. These numbers reference frequencies, or different pitches of sounds.
The frequency of a sound refers back to the frequency of vibration in the sound source. The faster the rate of vibration, the larger the frequency of the sound. Sound frequency is normally measured in Hertz (Hz). A 250 Hertz (250Hz) tone seems like an in-depth, low-pitched horn. A tiny, tinkling bell features 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 inside the range 250Hz to 8000Hz because a lot of the sounds of speech appear in this frequency range.
The intensity (loudness) of a sound is measured in decibels (dB). The decibel scale is shown along the side from the เครื่องช่วยฟัง. Audiologists want to use many 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 in the normally-hearing human ear.
The softest sounds that younger people with normal hearing can detect in ideal listening conditions, is between zero and 20 ( – 20) dB HL, across the frequency range.
Conversational speech measured from a single metre away is about 50 dB HL, though a number of the speech sounds is going to 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 loss increases as we get older. Over half the populace aged between 60 and 70 use a hearing difficulties. This increases to more than 70 % of those older than 70, and 80 per cent of those older than 80.
Hearing difficulties among veterans
War veterans are likely to have problems with hearing problems due to damage from noise exposure during their service. Hearing is definitely the second most frequent condition reported by Australian war veterans and war widows, with 55 per cent reporting hearing difficulties as a current condition.
What is masking?
In a hearing test, sound being sent to one ear can occasionally be heard through the opposite ear. This is usually only an issue if there is a positive change in hearing levels involving the two ears. Masking involves fpmaic an exclusive noise into one ear while testing another ear. Audiologists use masking to learn which ear (cochlea) is hearing the exam 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 get heard through the “better ear”, irrespective of which ear is nearest the loudspeaker.
Sound delivered by headphones or insert earphones is less probably be cross-heard. Masking is normally only needed if you have a significant difference in hearing levels in between the ears. Sound delivered by way of a bone conductor is readily cross-heard through the opposite ear. Masking is often required for bone conduction testing.