From da3b760f43266791266af7b6bbf8e4593fd41d6a Mon Sep 17 00:00:00 2001
From: Jeena <hello@jeena.net>
Date: Tue, 10 Mar 2026 02:22:10 +0000
Subject: [PATCH] audio: Apply square curve to volume slider
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AudioTrack.setVolume() takes a linear amplitude value, but human hearing
is logarithmic — a linear 0-1 slider sounds like all the volume is
crammed into the bottom quarter of the range. Squaring the slider value
(amplitude = linear²) spreads perceived loudness evenly across the
full slider travel.
---
 app/src/main/kotlin/net/jeena/pacer/AudioEngine.kt | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/app/src/main/kotlin/net/jeena/pacer/AudioEngine.kt b/app/src/main/kotlin/net/jeena/pacer/AudioEngine.kt
index 7017918..58f7b9e 100644
--- a/app/src/main/kotlin/net/jeena/pacer/AudioEngine.kt
+++ b/app/src/main/kotlin/net/jeena/pacer/AudioEngine.kt
@@ -22,6 +22,11 @@ class AudioEngine {
     companion object {
         private const val BEEP_DURATION_MS = 40
         private const val SILENCE_CHUNK_MS = 10
+
+        // Apply a square curve so the slider feels linear to human hearing.
+        // AudioTrack.setVolume() takes a linear amplitude; our 0-1 slider
+        // value is perceived as "all the volume at the bottom" without this.
+        private fun toAmplitude(linear: Float): Float = linear * linear
     }
 
     private val mainHandler = Handler(Looper.getMainLooper())
@@ -69,7 +74,7 @@ class AudioEngine {
             .setTransferMode(AudioTrack.MODE_STREAM)
             .build()
 
-        audioTrack?.setVolume(currentVolume)
+        audioTrack?.setVolume(toAmplitude(currentVolume))
         audioTrack?.play()
 
         handlerThread = HandlerThread("PacerAudio").also { it.start() }
@@ -94,7 +99,7 @@ class AudioEngine {
 
     fun setVolume(volume: Float) {
         currentVolume = BpmCalculator.clampVolume(volume)
-        audioTrack?.setVolume(currentVolume)
+        audioTrack?.setVolume(toAmplitude(currentVolume))
     }
 
     private fun audioLoop() {