10 dB SL is not the maximum, but anything above 20 dB SL is incredibly rare and almost unheard of. The highest I've personally seen reported is 30 dB SL. However, these numbers don't carry much weight, anyway, in the grand scheme of things.
From my experience, audiologists need far better training when it comes to tinnitus and how they talk to patients regarding it. This is completely anecdotal of course and I know there are some great ones out there, but of the many I have spoken to, they just weren't very knowledgeable.
Obviously, I wasn't there when the audiologist was talking to you, Tybs, so I don't know all the facts of what was said, but they should have explained that measuring tinnitus objectively is just not something we can currently do. At best we can estimate using the sensation level whilst doing a pitch and loudness match, but this cannot be compared to other decibel scale weightings. If this wasn't explained then I can understand why so many people are insulted when such a seemingly low number is given out. The reason for this is that most people try to compare their tinnitus to outside sounds using the A or C weighted decibel scales, and this will come to a much larger (and meaningless) number. I've spoken about this a number of times so I'll paste my previous message on this issue for further clarification to anyone who's interested:
There's no such thing as 70 dB tinnitus. You have to realise that there are many different weightings of the decibel scale and none of them really convert into something that can accurately measure how loud one's tinnitus is. There is the A-weighted scale which is aligned to the strongest frequencies within the human hearing range which is most notably 500 Hz to 8 kHz. Then there is the C weighted scale which takes in more of the lower and higher frequencies of a broadband sound. The Z rated scale is flat and measures all frequencies evenly.
The closest thing we have to measuring tinnitus is what's called a pitch and loudness match.
In audiology, you will see terms such as sensation level (SL) and hearing level (HL). Remember that the decibel scale is all relative to the quietest sound that can be heard, so when one has an audiogram and their hearing threshold shows 0 dB HL, this means they can hear the quietest sound that an average human ear can detect (assuming one has normal hearing and one is relatively young). This is where the HL standard is derived. Sensation level, on the other hand, is the measure of the intensity of an auditory stimulus above one's threshold at a given frequency. During a loudness match, the audiologist will find out at which frequency a person hears their tinnitus - if it's tonal - and then they will measure the distance between the loudness of that persons tinnitus and the threshold of their hearing. So for example, if a person hears tinnitus at 6 kHz at 40 dB and their hearing threshold at 6 kHz is 30 dB HL, then that person would have a tinnitus match of 10 dB SL.
One of the problems with this method is how accurately people can match their tinnitus to a frequency as there is often an octave error in one's judgement. This is especially true of people who have no musical training. The other issue with this is that it doesn't account for the brain's emotional processing of the sound which is the domain of Psychoacoustics. All sounds are not processed equally, and the volume we "hear" something at is the result of a complex chain of events within the brain. The more threatening a sound is perceived to be (which is based on our life's experiences) the louder it will be portrayed in our conscious awareness. You also have to factor in tiredness, adrenaline and other hormones, and many other factors. A great example of this is how a movie at the cinema is perceived as loud, but if someone so much as whispers, it can be annoying because it can be heard. The whisper that's heard in comparison to the volume of the movie is considerably quieter and yet people still hear it and get annoyed by it. Another example is how we can have our car stereo set at a comfortable level, only to find that it's LOUD the following morning when we are tired, even though nothing has changed. We often have our TV's on quietly at night, so as not to wake others up, and yet our brain can easily normalise this level of sound to be perceived as being louder. You discover this when you come to watch the following day and it's WAAY too quiet, so you turn it back up again.
What I'm saying is that our perception of sound is malleable and can change depending on the conditions we are hearing something in. A 20 dB creak in the middle of the night can potentially sound deafening if you are home alone.
From a Psychoacoustics point-of-view, two sounds that are the same on a decibel meter will not necessarily be perceived as being the same loudness, and for this reason, a new unit called the phon was created. A phon is equal to a decibel at 1 kHz, so 40 phons would be the same as 40 dB at 1 kHz. A 90dB sound at 150 Hz, for example, would not be perceived to be as loud as a sound that is 90 dB at 3kHz, so by using phons we can try and keep one's perception as neutral as possible. Sones are a linear representation of phons; 1 sone is equal to 40 phons and every 10 phons thereafter would represent a doubling in perceived loudness. This means that 50 phons would be equal to 2 sones and 60 phons would be equal to 4 sones, etc. Psychoacoustics is the science of how our brain interprets sound, and it's interesting to note that phons and sones are the primary units of measurement. This is because it's particularly difficult to define how loudness is perceived from one individual to another and these are likely the most neutral measurements we currently have.
This is already a long post, so I'll conclude by saying that most people's tinnitus is around 10 dB SL when using the pitch matching method. It's extremely rare to see anyone go above 20 dB SL.
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