---
title: "AirPlay Audio"
section: "smarthome"
tags: "smarthome"
parent: "/smarthome/"
description: "Multi-room AirPlay receivers with software volume boost on Raspberry Pi devices."
layout: base.njk
---
<h1>AirPlay Audio</h1>
<div class="detail-content">

<p>Two Raspberry Pis run AirPlay receivers so any Apple device in the flat
can stream audio to the kitchen or the bathroom without a dedicated
speaker app.</p>

<h2>Setup</h2>
<table>
<tr><th>Location</th><th>Hardware</th><th>AirPlay version</th><th>Runs as</th></tr>
<tr><td>Kitchen</td><td>Raspberry Pi 3B</td><td>AirPlay 2</td><td>Docker container (shairport-sync)</td></tr>
<tr><td>Bathroom</td><td>Raspberry Pi Zero W</td><td>AirPlay 1</td><td>Native systemd service (older OS, legacy repo)</td></tr>
</table>

<h2>The volume-boost problem</h2>
<p>Both Pis' analog audio output is too quiet at full hardware volume, so
a software mixer stage (<code>+20&nbsp;dB</code> via an ALSA softvol plugin) sits between
shairport-sync and the hardware. The hardware mixer itself is deliberately
left fixed at 100% / 0&nbsp;dB, and shairport-sync only ever adjusts its own
internal software volume — this avoids the volume jumps and mixer
conflicts that show up when multiple layers all try to control loudness.</p>

<h2>Bathroom-specific integration</h2>
<p>The bathroom Pi also runs a small custom tool that starts an internet
radio stream automatically when its light sensor detects the light has
been switched on. A simple flag file signals whether AirPlay is currently
active, so the automatic radio stream politely stays off while someone is
actively AirPlaying — and resumes its normal behavior as soon as the
AirPlay session ends.</p>

<h2>Why this design</h2>
<ul>
<li>Software-only volume control avoids ALSA mixer conflicts across two different loudness sources.</li>
<li>The flag-file handoff is trivial to implement and doesn't need a message broker for something this simple.</li>
<li>Docker on the kitchen Pi keeps that receiver easy to update; the bathroom Pi's older OS made a native install more reliable than fighting Docker on legacy hardware.</li>
</ul>
</div>