The audiogram records the softest level of sound an individual detects at each frequency, in accordance with specific test criteria. These detectable degrees of sound are known as the person’s hearing thresholds. In 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.
Glance 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 the sound refers back to the frequency of vibration in the sound source. The faster the pace of vibration, the larger the frequency of the sound. Sound frequency is normally measured in Hertz (Hz). A 250 Hertz (250Hz) tone looks like an in-depth, low-pitched horn. A small, 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 in the range 250Hz to 8000Hz because most of the sounds of speech appear in this frequency range.
The intensity (loudness) of the 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, 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 from the normally-hearing human ear.
The softest sounds that young adults with normal hearing can detect in ideal listening conditions, is between zero and 20 ( – 20) dB HL, throughout the frequency range.
Conversational speech measured from one metre away is about 50 dB HL, though some 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, using 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 while we grow older. Over half the population aged between 60 and 70 have a hearing loss. This increases to more than 70 percent of the over 70, and 80 % of the over 80.
Hearing loss among veterans
War veterans will probably have problems with hearing problems due to damage from noise exposure throughout their service. Hearing is the second most common condition reported by Australian war veterans and war widows, with 55 % reporting hearing problems as a current condition.
Precisely what is masking?
Throughout a hearing test, sound being sent to one ear can often be heard through the opposite ear. This is usually only a problem if there is a positive change in hearing levels in 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 young kids are tested with sounds played away from a loudspeaker, the sound is assumed to get heard from 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 usually only needed if there is a big difference in hearing levels in between the ears. Sound delivered with a bone conductor is easily cross-heard from the opposite ear. Masking is often required for bone conduction testing.