Audio pipeline in depth

This chapter explains how an uploaded sound file ends up playing for the right participant. You set the pieces up in Step 6 · Audio. The examples use the Acoustic Ripple Therapy scheme (see About the trial).

The building blocks

Sound type

The category of modulated sound, taken from the participant’s current arm. ART uses Amp and Phase (with Amp+Phase and Loc planned).

Hearing profile

A preset describing the participant’s hearing. ART uses four: None, Mild, Mod, Sev.

Modulation band

The frequency band a sound is modulated in. ART currently uses seven bands ranging from 1 to 2 kHz up to 8 to 16 kHz. An unmodulated sound (for a washout-unmodulated arm) has no band.

Matching a participant, step by step

Before treatment, the participant is personalised through a short in-app process:

1. Hearing profile. They listen to four pure-tone sequences (PT_None, PT_Mild, PT_Mod, PT_Sev) and pick the one with the most consistent volume. That choice sets their hearing profile.

2. Tinnitus type. They compare a pure-tone (PT) and a narrowband-noise (NBN) sequence for their profile and pick whichever is more like their tinnitus. This feeds frequency matching but not the final sound choice.

3. Frequency match. They adjust a frequency scale to find the tone closest to their tinnitus. The matching sounds are named {Type}_{Hearing}_{Freq}, for example PT_Mild_2.8; the participant only sees the frequency, because type and hearing are already set.

From the match to the sound they hear

The trial’s assignment table turns the participant’s matched tinnitus frequency into the modulation band they receive. Each frequency has an active band and a placebo band; which column applies is set per arm (active arms read the active column, sham arms read the placebo column).

The therapeutic sound is then the file matching three things: the arm’s sound type, the participant’s hearing profile, and that modulation band. Files follow the naming convention:

{SoundType}_{HearingProfile}_{ModBand}

for example Amp_Mod_2-4. Unmodulated sounds have no band.

Example assignment table

The table below is the example ART assignment. A participant matched at 2.8 kHz gets a 2-4 band on the active arm and 4-8 on the sham arm.

Tinnitus match (kHz)	Active band (kHz)	Placebo band (kHz)
1.0 / 1.2 / 1.4	1-2	2-4
1.7 / 2.0	1.4-2.8	2.8-5.7
2.4 / 2.8	2-4	4-8
3.4 / 4.0	2.8-5.7	5.7-11
4.8 / 5.7	4-8	2-4
6.7 / 8.0 / 9.5	5.7-11	2.8-5.7
11.0 / 13.0 / 16.0	8-16	4-8

The assignment table is a trial-level setting, so a future trial could use a different mapping.

Coverage

Because a participant could fall into any combination of hearing profile and modulation band, Step 6 · Audio shows a coverage summary per sound type: how many of the expected hearing-profile by modulation-band combinations you have uploaded, so gaps are visible before launch. Sound files are around 60 minutes each; a lossless format is preferred where space allows.