.... it's not going to increase the volume of the sounds that hurt? I was wondering about this before - I'd hate to have the high pitched sounds that still hurt my ears a bit increased in volume!
click -
That's a very good question.
(Let me find my Danny Kaye professor's hat ...I know it's around here somewhere...Yeah, there it is. Ok, let's get on with the show!)
The sound we hear is a complex mixture of pure sinusoidal tones. Tinnitus is usually a pure tone. Many researchers are of the opinion that tinnitus is caused by a voltage from an efferent nerve associated with the sinusoidal pure tone.
Here's how it works:
1. Complex sound goes into the cochlea.
2. The sound is absorbed along the length of the cochlea. The high pitched frequencies are absorbed at the beginning of the cochlea. The low pitched frequencies are absorbed near the end.
3. When we listen to complex sounds, it is de-composed into simple sinusoidal frequencies along the length of the cochlea in the above manner. For example, every now and then, 4kHz may be a part of the complex sound. We don't hear a constant 4kHz.
We hear 4kHz
only now and then, whenever it occurs as a part of a complex sound.
4. Cochlear hairs convert vibrations into voltages to the nerves. The voltage creates a current in the afferent nerves leading to the brain (the "inferior colliculus"). The brain receives the voltage from the afferent nerve. The brain then "experiences" that a vibration is occuring at the ear.
All nervous circuitry has the following closed loop:
Stimulus (carried by afferent nerves) -> Decision (brain) -> Reaction (carried by efferent nerves)
Whether the nerves are carrying information about sound, skin temperature or sight, they carry this information by sending synaptic currents. The brain recieves this voltages in mapped areas, perceiving these as sound, skin temperature or sight, etc.
(Amazingly, researchers can elicit sensory experiences simply by applying voltages to areas of the brain!)
5. When you have hearing loss, it's due to cochlea hair damage/loss. The damage is usually more so in one ear than the other, setting up an imbalance. Let's say you have 4kHz loss in your right ear as a result of damage/loss of cochlea hairs at the 4kHz location. Then, when you are hearing a complex sound, the healthy left ear sends 4kHz (
every now and then as part of a complex sound) to the superior ollivary complex, but the right sends nothing.
6. When
the superior ollivary gets this information, "4kHz from left, zero from right", it
reacts to this imbalance and sends a signal along the efferent nerve to the right to "crank it up".
7. This "crank it up" signal happens repeatedly, and becomes an errant signal. In effect, the right ear tries to listen harder and harder in response to "crank it up" from the efferent nerve. This causes a feedback loop. The right ear is not actually hearing 4kHz.
It is a signal from the efferent nerve that the ear with the associated hearing loss is perceiving as a real sound.
It's basically a defective, unbalanced circuit that has feedback. The right ear, which can't hear 4kHz naturally, is "hearing" the efferent nerve's signal
all the time!
When you use a hearing aid, the hearing aid decomposes a complex sound into simple tones. The hearing aid is able to amplify only the tones where there is hearing loss. The superior ollivary complex will then get 4 kHz from the good ear and, more or less, sidebands near 4kHz from the bad ear with the hearing aid. The system perceives this as a naturally "balanced" system. In response, it no longer sends a signal to the efferent nerve back to the ear to "crank it up". Without a signal from the efferent nerve, tinnitus should go away.
(now I'll put my hat away...)
Member
) - just waiting a while before I do to see if it goes away on its own. I was referred to an audiologist after seeing a GP about the T in Cornwall but I was in France by the time the appointment arrived so didn't go. Not sure that I'd trust them to get it right.. that's the problem. What if hearing everything louder made my T worse... especially as I haven't got any hearing problems - just normal marginal high pitch loss. Confusion, confusion - what causes it.. what makes it worse.. what should I be doing/not doing.. indecision... talk about going round in circles!
