What is diplacusis?
To understand this condition, it is necessary to understand the way the brain processes sounds. Sounds coming from one direction can come into one ear at one pitch and the other ear at a slightly different one. The brain automatically adjusts for this and the person perceives the two pitches as a single sound. However, with certain conditions of the ear, the sounds start coming in as two completely different tones. The brain does not combine them so it sounds like there are two signals when there is actually only one. This condition is what doctors call diplacusis.
This condition often happens suddenly after an ear infection, head trauma, or exposure to loud sound. Those more sensitive to sound, like musicians, may recognize the problem before others. One ear may hear a tone at its pure tone. The other ear can come in a half-tone higher or lower than the other. Sometimes, the difference is more significant than a half-tone. The brain does not know which one to process so it allows both in as two different signals.
What is happening in the ear with diplacusis?
Each human ear has a frequency range that it hears. Normal human hearing runs from 20 Hz to 20000 Hz, but individual people’s hearing can vary. As people age, the ears may lose the ability to hear at the highest range. For a person with normal hearing, both ears have about the same hearing range. However, when one ear loses its frequency range at a greater amount than the other one, it causes signal problems in the brain.
For example, if the left ear hears a tone as D, the right ear may hear the same tone as a D-sharp (D#) or E. Due to the significant difference in tones, the brain processes the signals as being two different sounds.
Are there different types of diplucusis?
There are four recognized types:
- Diplacusis binauralis – The person hears sounds differently in each ear. One ear may register a different pitch or a different timing of the sound.
- Diplacusis dysharmonica – This condition is a subset of diplacusis binauralis. It refers to only the pitch being different in the ear. Some doctors refer to this as “Interaural Pitch Difference.” It is the most common form.
- Diplacusis echoica – The timing of tones is slightly different in one ear. So, the same sound registers as an echo.
- Diplacusis monauralis – The person perceives the same sound as two different ones in the same ear.
What causes diplacusis?
Injury and infection are the leading causes of this medical condition. However, other conditions, like wax build-up, can also cause this problem.
What treatment options are available for diplacusis?
Clearing up the difference in frequency between the two ears is the best option.
Treating an infection, unclogging sinuses, and cleaning out ear wax can ease the problem. As the problem clears, hearing should return to normal. For those who have a hearing loss due to other conditions, hearing aids can even out the frequency ranges in both ears and relieve the diplacusis. In some cases, however, no treatment will reduce the problem.
Knowing about diplacusis is the first step to doing something about it. If this condition sounds familiar to your symptoms, talk with your doctor. Testing can show if there is a problem and give doctors a path for treatment.
Tom Regev is a professional writer for the Hearing Aids American Fork branch.