The audiogram records the softest level of sound someone 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 usually attempt to obtain thresholds for many different frequencies in each ear, often using various ways (air conduction and bone conduction) to deliver the sound to the ear.
Consider the blank audiogram graph below. Along the top of the the graph the numbers vary from 125 to 8000. These numbers reference frequencies, or different pitches of sounds.
The regularity of any sound refers back to the frequency of vibration in the sound source. The faster the pace of vibration, the greater the frequency of the sound. Sound frequency is usually measured in Hertz (Hz). A 250 Hertz (250Hz) tone seems like a deep, low-pitched horn. A small, tinkling bell has a high-pitch sound, probably measuring around 3,000 to 4,000 Hz.
Normal, healthy, young human ears can hear frequencies only 20Hz and as much as 20,000Hz. However, audiologists test hearing inside the range 250Hz to 8000Hz because most of the sounds of speech happen in this frequency range.
The intensity (loudness) of any sound is measured in decibels (dB). The decibel scale is shown along the side from the เครื่องช่วยฟัง. Audiologists want to use a variety of decibel scales, for the way the sound is measured. For hearing tests, sound is usually measured in decibels of Hearing Level (dB HL). This decibel scale reflects the sensitivity in 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, across the frequency range.
Conversational speech measured from one metre away is about 50 dB HL, though a number of the speech sounds will be around 35 to 40 dB HL.
Conversational speech measured from four metres away will be quieter, about 35 dB HL, with all the softer speech sounds only measuring around 20 dB HL.
Really loud rock concerts can measure 110 to 120 dB HL. Many people find sounds over 100 dB HL unpleasantly loud. The incidence of hearing loss increases while we grow older. Over half the population aged between 60 and 70 use a hearing difficulties. This increases to greater than 70 per cent of those older than 70, and 80 per cent of the over 80.
Hearing difficulties among veterans
War veterans will probably suffer from hearing problems due to damage from noise exposure throughout their service. Hearing is the second most frequent medical problem reported by Australian war veterans and war widows, with 55 per cent reporting hearing difficulties being a current medical problem.
What exactly is masking?
Throughout a hearing test, sound being sent to one ear can often be heard by the opposite ear. This is usually only a concern when there is a change in hearing levels between the two ears. Masking involves fpmaic a unique noise into one ear while testing one other 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 from a loudspeaker, the sound is assumed to become heard through the “better ear”, regardless of which ear is nearest the loudspeaker.
Sound delivered by headphones or insert earphones is less apt to be cross-heard. Masking is generally only needed if you have a huge difference in hearing levels in between the ears. Sound delivered by way of a bone conductor is easily cross-heard by the opposite ear. Masking is frequently necessary for bone conduction testing.