The audiogram records the softest level of sound someone detects at each frequency, based on specific test criteria. These detectable degrees of sound are known as the person’s hearing thresholds. In a hearing test, the audiologist will often make an effort to obtain thresholds for a number of different frequencies in each ear, often using various ways (air conduction and bone conduction) to deliver the sound to the ear.
Glance at 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 rate of vibration, the larger the frequency of 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 includes 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 high as 20,000Hz. However, audiologists test hearing in the range 250Hz to 8000Hz because the majority of the sounds of speech occur in this frequency range.
The intensity (loudness) of a sound is measured in decibels (dB). The decibel scale is shown on the side in the เครื่องช่วยฟัง. Audiologists need to use many different decibel scales, depending on how the sound is measured. For hearing tests, sound is usually measured in decibels of Hearing Level (dB HL). This decibel scale reflects the sensitivity from 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, throughout the frequency range.
Conversational speech measured in one metre away is about 50 dB HL, though some 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 as we age. Over half the population aged between 60 and 70 possess a hearing difficulties. This increases to greater than 70 percent of these older than 70, and 80 percent of these over 80.
Hearing difficulties among veterans
War veterans will likely have problems with hearing problems because of damage from noise exposure during their service. Hearing is the second most frequent medical problem reported by Australian war veterans and war widows, with 55 % reporting hearing problems as being a current medical condition.
Precisely what is masking?
During a hearing test, sound being sent to one ear can sometimes be heard through the opposite ear. Normally, this is only an issue if there is a difference in hearing levels between the two ears. Masking involves fpmaic an exclusive noise into one ear while testing one other ear. Audiologists use masking to find out which ear (cochlea) is hearing the test sound.
Sound heard in a room reaches both ears at very similar levels. When very young kids are tested with sounds played from a loudspeaker, the sound is assumed to get heard by the “better ear”, irrespective of which ear is nearest the loudspeaker.
Sound delivered by headphones or insert earphones is less apt to be cross-heard. Masking is normally only needed if there is a significant difference in hearing levels between the ears. Sound delivered with a bone conductor is readily cross-heard from the opposite ear. Masking is often needed for bone conduction testing.