From 5797c4275344f89f7db2197cf880c9c0ce210eb4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mart=C3=ADn=20=28Netux=29=20Rodr=C3=ADguez?=
 <send.email@netux.site>
Date: Tue, 3 Sep 2024 17:58:52 -0300
Subject: [PATCH] Calculate global gain with a better approximation of human
 perceived loudness

Taken from https://www.dr-lex.be/info-stuff/volumecontrols.html
---
 website/src/repl/util.mjs | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/website/src/repl/util.mjs b/website/src/repl/util.mjs
index c4aece189..2b1b4d9d3 100644
--- a/website/src/repl/util.mjs
+++ b/website/src/repl/util.mjs
@@ -194,10 +194,16 @@ export const setAudioDevice = async (id) => {
   initializeAudioOutput();
 };
 
+const NATURAL_LOG_10 = Math.log(1000);
+const LOW_VOLUME_CONSTANT = Math.exp(0.1 * NATURAL_LOG_10);
 export const setGlobalAudioVolume = (volume) => {
-  // Adjust user visible volume to a gain value in the range [0, 1]
-  // Pow is used to also adjust the volume to a logarithmic scale (as perceived by us humans)
-  const gain = Math.pow(volume / 100, 2);
+  // Gain is calculated to adjust the volume to a logarithmic scale to match how us humans perceive loudness.
+  // Formula is taken from https://www.dr-lex.be/info-stuff/volumecontrols.html
+  volume /= 100; // [0, 1]
+
+  let gain = volume >= 0.1 ? 0.001 * Math.exp(NATURAL_LOG_10 * volume) : volume * 10 * 0.001 * LOW_VOLUME_CONSTANT;
+  gain = Math.max(0, Math.min(gain, 1)); // just in case
+
   setGlobalGain(gain);
 };