The audiogram records the softest level of sound someone detects at each frequency, in accordance with specific test criteria. These detectable levels of sound are known as the person’s hearing thresholds. In a hearing test, the audiologist will most likely make an effort 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 from 125 to 8000. These numbers reference frequencies, or different pitches of sounds.
The frequency of any sound means the frequency of vibration in the sound source. The faster the pace of vibration, the higher the frequency from the sound. Sound frequency is generally measured in Hertz (Hz). A 250 Hertz (250Hz) tone sounds like a deep, 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 low as 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 any sound is measured in decibels (dB). The decibel scale is shown along the side from the เครื่องช่วยฟัง. Audiologists need to use a number of 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 of 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 approximately 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. Many people find sounds over 100 dB HL unpleasantly loud. The incidence of hearing loss increases as we grow older. Over half the populace aged between 60 and 70 possess a hearing problems. This increases to more than 70 percent of those older than 70, and 80 percent of those over the age of 80.
Hearing problems among veterans
War veterans will likely are afflicted by hearing problems due to damage from noise exposure during their service. Hearing will be the second most typical medical condition reported by Australian war veterans and war widows, with 55 % reporting hearing loss being a current condition.
What is masking?
In a hearing test, sound being shipped to one ear can often be heard by the opposite ear. Normally, this is only a concern if there is a difference in hearing levels involving 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 out of 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 likely to be cross-heard. Masking is normally only needed when there is a big difference in hearing levels between the ears. Sound delivered with a bone conductor is definitely cross-heard from the opposite ear. Masking is usually necessary for bone conduction testing.