Hearing test

Suppose a person goes to the doctor to get their hearing checked. The doctor plays a 300 Hz tone at increasing SPL (starting from 0 dB), asking the patient to raise her hand when she first perceives the sound. She raises her hand when the SPL is at 60 dB. Does the patient have a hearing loss? And if so, what is the amount of hearing loss of this person? Explain your answer.  [Hint: you may want to check the Fletcher-Munson diagram.]

More to read: Vision and Hearing

Build your own audibility threshold curve! Here’s how you can do it. Go to this hearing test online site (Links to an external site.)Note: you will need to open this on Chrome. If you don’t have Chrome on your computer, you can download it from here (Links to an external site.). You will also need to allow this site to use Flash. Here (Links to an external site.)are instructions (click on “Allow sites to use Flash”). Read the instructions in the hearing test online site.

Remember how we used this tool in class (1022/20 lecture): each little tile in the matrix is associated with a short “tone” at a given frequency and given SPL (in dB). If possible, use a headphone, and remember to always start from the lowest SPL tones (those in the lower rows of the matrix). Set the volume of your system so that you can comfortably hear a 1 KHz tone at mid-level (in the middle row of the matrix).

Then try the 1 KHz tone with lower SPL, until you can barely hear it (meaning that if you try one row below, you cannot hear it anymore). Assuming your hearing is OK, this corresponds to an SPL of 0 dB. Now: note the dB scale to the left is deceiving. It does not read “0 dB” for this “barely audible” 1 KHz tone, as we would expect it to do – it may read, for example, “- 78 dB”. Why this discrepancy? This is because the SPL of the sound that you are hearing depends on the volume setting of your system! In other words, the same tile in the matrix generates different SPL depending on the volume of your system.

So what we need to do is to adjust the dB value we read from the matrix so that your barely audible 1 KHz sound becomes 0 dB. In the example below, we would simply have to add an offset of 78 dB to it (-78 dB + 78 dB = 0 dB). And, you would have to add the same value (in this case, 78 dB), to all SPL measurements that you will report. Now, your task is to build your full audibility threshold curve. That is, you need to test all other frequencies in the matrix, trying different SPLs until the sound for that frequency is barely audible.

Then read the value of SPL and add the same offset you found for the 1 KHz tone – in the example above, 78 dB. There you go – you have generated your audibility curve, which is made by the SPLs (corrected for the offset) of the barely audible tones at all different frequencies. For each frequency (in Hz), you have an offset-correct SPL in dB (i.e., the SPL you read in the matrix, plus the fixed offset.) Now: you will need to produce a plot of the result. The plot must have frequencies (in Hz) in the X axis, and the offset-corrected SPL of barely audible tones (in dB) in the Y axis.

You could use Excel, if you are familiar with it, or Google Sheets (Links to an external site.), or an online plotting tool such as this one  (Links to an external site.)(choose the Bar type of plot). Make sure to save the plot and attach it to your homework.

Now try your speech discrimination abilities here (Links to an external site.): Click on the “speech-in-noise test” link. You will be directed to adjust the volume to the desired level. Then you can do a practice test, if you want, or just skip it and go to the real test. Your goal is to write down the 3-digit number that is being read. Write your hearing result at the end of the test.

Last Updated on November 19, 2020

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