Teensy audio board

[13_96]

Hi…
Can a Teensy audio board be used for amplification, filtering, noise cancellation applications?
What is the maximum gain it can give? Can it be used for amplification greater than 140 dB SPL ?

[chipaudette]

Yes, the Tympan can be used for amplification and filtering, as examples are provided in the examples directory in the Tympan_Library.

It could also be used for noise cancellation, though that is a very broad term, so I cannot know whether the Tympan is fast enough to run your particular noise cancellation idea.

Finally, the maximum SPL is dependent upon the ear phones or speakers that you attach. The Tympan headphone amplifier (part of the Texas Instruments 3206 AIC inside the Tympan) is limited to something like 0.1W of output power. I think that you’ll have a hard time finding a speaker that is sensitive enough to generate 120 dB SPL for only 0.1W of power from our amplifier. So, 140 dB SPL is probably out of reach.

Please be aware that 140 dB SPL is an extremely dangerous sound level. I do not recommend experimenting with any system that is capable of generating this sound intensity, unless you have very carefully considered your safety protections.

Chip

[13_96]

Thank you for your reply.

I wanted to know which degree of hearing loss does tympan open source hearing aid design aim at? Is it mild, moderate or severe profound?

I am planning on using knowles series microphone and receivers using tympan audio board. What are the limitations in choosing microphone and receivers? What are the specifications that are to be considered while selecting microphone and receiver compatible with tympan audio board?

[chipaudette]

Hi!

To be clear, the Tympan is a device to help with research and experimentation, not to provide treatment for hearing loss. If someone is looking to treat someone with hearing loss, one should consult with an audiologist or other medical professional.

But, if you are looking to do research, the performance of the Tympan is very dependent upon the performance of the microphone and speaker (receiver) used with the system.

For example, if you use lapel microphones instead of hearing aid microphones, you often lose 20dB in potential gain simply because the lapel mics are much less sensitive and have a higher self-noise floor. Here’s a comparison of three microphones:

Calibrating Microphones with Tympan

In the post above, the “Knowles” mic is one intended for use in a hearing aid and it is much better than the other microphones if moderate to high gain is needed.

I believe that a similar difference exists with respect to the speakers/receiver. A hearing aid receiver (I believe) mounted in an earpiece produces much more output than a typical ear bud or ear phones. I have not tested with a a hearing aid receiver, though, so I cannot confirm this. I have only tested with consumer ear buds:

Calibrating My Earphones with the Tympan

A fellow forum member tested with other brands of ear buds, as well:

Electroacoustic Evaluation, Part 2 (Flat Gain, No Compression)

##Electroacoustic Evaluation (Flat Gain, No Compression) To further evaluate the frequency response of the Tympan unit, the code (‘BasicGain’) was set to amplify the broadband signal by 20 dB without frequency shaping or compression of any sort. Gain was further adjusted by another -10 to +20 dB via the volume control knob. Three tests were conducted. First, the response to 90-dB SPL broadband pink noise was obtained for -10, 0, +10, and +20 dB volume settings. Second, the response to 90-dB…

To answer your broader question, what level of hearing loss are we aimed at, that’s a difficult question given that it is dependent upon the mics and receivers used. For the configurations that we’ve tested (lapel microphones with consumer ear buds), I’m typically running at somewhere around 25-35 dB of gain in SPL.

Hopefully I’ve been helpful.

Chip