# About the trial

The portal is general-purpose, but it was built for a specific study: the **Acoustic
Ripple Therapy (ART)** tinnitus trial. This page describes that trial so the rest of the
manual has a concrete example to point at. Your own trial may differ; the portal
supports the same shape of design with different numbers.

## The therapy

Participants listen to a personalised therapeutic sound for around **60 minutes a day**.
The sound is matched to the participant's hearing and tinnitus (see
{doc}`audio-pipeline`), and is modulated in a specific frequency band. The **active**
therapy uses the modulation band intended to help; the **sham** uses a control band, so
the two are indistinguishable to the participant but only one is therapeutic.

## The design: a randomised crossover

ART is a **randomised, placebo-controlled crossover**:

1. Each participant is randomly allocated to start in either the **active** or the
   **sham** group.
2. They complete a **treatment period** (this trial: **6 weeks**, roughly 60 minutes of
   listening per day).
3. A **washout** follows (this trial: **3 weeks**), during which there is no listening
   but participants still give a daily tinnitus rating.
4. They then **cross over** into the opposite group and repeat the treatment period.

Because every participant experiences both conditions, each person is their own control.
Which condition they had at which time is revealed only at the **debrief** at the very
end (see {doc}`participants-lifecycle`).

:::{admonition} Bigger designs
:class: note
This trial uses two arms and two treatment periods, but the portal supports more: up to
several intervention periods with washouts between them, and additional arms. You build
that shape in {doc}`setup/4-schema`.
:::

## What a participant does

1. **Register and consent** (a short unlock delay, then the consent form).
2. **Screening** to confirm eligibility (see {doc}`assessments`).
3. **Baseline questionnaires** (THI, TFI, IHS).
4. **Hearing profile and tinnitus matching** to personalise the sound.
5. **Treatment period 1** with daily listening and before/after ratings.
6. **Washout 1** with daily ratings and washout questionnaires.
7. **Treatment period 2** (the opposite arm) and its ratings.
8. **Final washout, end questionnaires, and debrief.**

The chapters that follow explain each of these from the researcher's side: how you
configure them, and what the participant sees.