Contents

1 Not everyone hears the same

The ToH curve [1] varies between individuals:

1. In general, women hear better than men.
2. With age, we lose sensitivity to high frequencies.
3. Exposure to loud noises over time can elevate the ToH, especially in individuals exposed to loud sound.
4. Auditory training can help detect sounds at lower intensities or distinguish subtle nuances in tone.

And this can be said without considering your local audio infraestructure.¹

Therefore, it is quite improbable that, at least in practice, you have a ToH identical to the theoretical curve shown in the previous milestone.

2 Why to use custom ToH curves?

If you are talking to a semi-deaf interlocutor, why would you send them auditory information that they will not be able to perceive? For this reason, this step proposes the calculation of your own ToH curve, information that must be transmitted to your interlocutor so that they can use the quantization steps adapted to your perception.

3 A procedure to determine your YoH curve

An optimal-user-specific ToH should take into consideration your noticeable quantization noise in each subband, defining a set of QSSs (one per subband). To find such set, the following algorithm can be used:

1. Starting with the lowest frequency subband (at the first iteration the rest of subbands are zero). While the noise (suppose that the quantization noise follows an uniform distribution) is imperceptible:

   1. Increase the amplitude of the noise in the subband.
   2. Compute the inverse transform, generating a chunk of audio.
   3. Reproduce the generated chunk, alternating every second with a silence (the play of an empty chunk).
2. Continue with the next subband, but keeping the highest unperceptible noise in the previously processed ones.

It’s a good idea to have the option of determining the ToH of a given subband, without reconsidering the rest of them.

4 Deliverables

Implement the previous procedure in a Python module named create_ToH.py. The output of such module should be a text file, named custom_ToH.txt, with three columns (example):

# Initial_frequency_in_Herts Band-width_in_Herts ToH
20                           50                  100
70                           60                  80
130                          80                  60
210                          100                 50
310                          150                 40
460                          180                 30
:                            :                   :

Modify the modules *_ToH.py to use the file custom_ToH.txt, when available.

Mark: 8 points.

5 Resources