In this instructable, we will be building an intelligent hearing aid. The goal is to build a low power, cost-effective hearing aid that has several key intelligent features. First, it has tuning functionality that allows the wearer to tune the amplification to his or her needs. It has a conversational mode which recognizes voice input and amplifies it while reducing background noise. It saves all data to memory so that the device can be quickly powered up and ready to use. This device also has a very easy user interface to keep operation quick and simple.

The block diagram above outlines how the hearing aid works. A signal picked up by the microphone first goes through a pre-amp stage which culls frequencies above 3kHz (outside hearing spectrum) and then amplifies the remaining signal for future stages. The signal then progresses to the filter stage where it goes through four parallel filters that divide the signal into four frequency ranges. This filtered signal is read by the level estimator and provided to the Arduino. The filtered signal is also passed to the gain-controlled stage where the signals are amplified based on tuning settings provided by the Arduino. The signal finally enters the output stage where it passes through a summer and the modified signal can be heard with a pair of earphones.

Step 1: Design

The circuit for the hearing aid must accomplish several key tasks. First it has to amplify the microphone signal to a large enough level to be processed by the rest of the circuit. Next the signal has to be passed through a set of filters to split up the signal into four audio bands to be level estimated and then individually scaled. Finally the bands must be recombined and sent to a pair of headphones. The Arduino reads the levels of each band and scales the bands appropriately.

This project requires about $60 worth of parts. See cost table above. Please refer to the parts list attached for a full list.

<p>A very cool project. I learned a ton building it. Unfortunately, mine does not work. I can hear a very, very low signal from the mic and that is about it. Can't seem to get the Arduino to properly tune or go into the conversational mode. Frustrating because I know I am so close! Sigh. Thanks all the same to ojoshi for the interesting project though!</p>
<p>An excellent design Instructable. Very educational.</p><p>The author should have noted that a clear schematic (<a href="https://www.instructables.com/files/orig/F6G/KLAQ/HOUFWVN1/F6GKLAQHOUFWVN1.sch" rel="nofollow">final_schematic.sch</a>) can be opened in Eagle. Then everything is legible, and all components are defined in the bill of materials (<a href="https://www.instructables.com/files/orig/F2V/3YWP/HOUFWVN0/F2V3YWPHOUFWVN0.xlsx" rel="nofollow">final_bom.xlsx</a>).</p><p>The next step is to downsize it for wearing (no easy task).</p>
<p>What wattage resistors should I use for this project?</p>
<p>is there any how to do tutorial for this project</p>
<p>Looks like final_schematic.sch is empty because if I open it with Altium Designer it looks emtpy...do you have a good one? Thanks</p>
<p>Its amazing project , but what about values !!!! please provide us with the values in the circuit to try it as senior project .</p>
<p>am interested in this project but i can see the values, pls help me out here.</p>
Useless... Cant read the values from the picture
<p>This is awesome! My grandfather has an estimated 80% hearing loss. Traditional hearing aids don't work well for him as they amplify everything. I'm going to attempt to build this. Than you so much for sharing!!</p>
Thanks a lot for this posting. I'm hearing impaired, with permanently variable unheard frequencies (every day is different). I'll give this a try.
Cool project! I'll bookmark it for future use. Thank you.

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