A hearing test helps to determine both if someone has a hearing loss and the severity of the hearing loss. The results are recorded on a chart called an audiogram. The pure tone audiogram is a graph which shows the pitches (frequencies) across the top and the loudness (intensity) down the side. In general, the audiogram indicates how loud different sounds must be before they are first heard. The pure tone audiogram is filled out by an audiologist to indicate the degree of hearing loss.
Frequency
We hear across a wide range of sound frequencies or pitches. Notes from a bass drum, a deep male voice or vowel sounds are low-pitched sounds and register at the left side of the audiogram. Conversely, notes played on a flute, women’s and children’s voices and many consonant sounds such as ‘s’, ‘t’, ‘f’, ‘sh’, are high pitched sounds and register at the right side of the audiogram.
250 Hz (Hertz) is a low frequency sound and 8000 Hz is a high frequency sound. In other words, the lower the number, the lower the pitch of the sound.
The range of 250 to 8000 Hz represents the frequencies most useful for listening to speech, which is why audiologists test through this range. The “speech banana” on the audiogram has been added to show where most conversations occur in terms of loudness and pitch.
Intensity
The numbers down the side of the audiogram represent intensity or loudness and are measured in decibels or dB. The greater the sound, the greater the number of dB. Zero is very faint. Breathing has a level of approximately 10 dB HTL.
A circle (O) represents the right ear and a cross (X) represents the left ear response when testing is completed under ear phones (air conduction testing). You may also see some other markings on the audiogram that look like this: < or >. These markings are used when testing is completed with a black vibrator placed over the mastoid bone behind the pinna of the ear. It represents the results obtained by bone conduction testing. Comparing bone conduction results with the air conduction results gives the audiologist some important information about the nature of the hearing loss – conductive, sensori-neural or mixed.
The audiogram of a person without hearing loss would show hearing at all frequencies between -10 to 26 dB HTL. All recordings on the audiogram greater than 26 dB HTL represent a hearing loss at that frequency.
In summary, the audiogram tells us how loud (in dB HTL) a sound must be to be heard at different pitches (Hz) and it also gives us some idea about the nature and degree of the hearing loss.
Your audiologist should answer all your questions and review any results and recommendations with you.