From 90fe37ae4b0b5026a3f09e9050556237069c1e52 Mon Sep 17 00:00:00 2001
From: Paul Adenot <paul@paul.cx>
Date: Thu, 5 Nov 2026 14:53:19 +0100
Subject: [PATCH 1/2] Clarify that PeriodicWave real[0] is ignored

The constructor sets index 0 of real and imag to 0, so a PeriodicWave
cannot produce a DC-offset. Point authors to ConstantSourceNode instead.

Closes #2530
---
 index.bs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/index.bs b/index.bs
index 08becf433..30cdb7127 100644
--- a/index.bs
+++ b/index.bs
@@ -10002,8 +10002,10 @@ Dictionary {{PeriodicWaveOptions}} Members</h5>
     : <dfn>real</dfn>
     ::
         The {{PeriodicWaveOptions/real}} parameter represents an array of
-        <code>cosine</code> terms. The first element (index 0) is the
-        DC-offset of the periodic waveform. The second element
+        <code>cosine</code> terms. The first element (index 0) is
+        ignored: it is set to 0 when the {{PeriodicWave}} is constructed,
+        so a {{PeriodicWave}} cannot produce a DC-offset. A DC-offset can
+        be added by connecting a {{ConstantSourceNode}}. The second element
         (index 1) represents the fundamental frequency.  The
         third represents the first overtone and so on.
 </dl>

From d17ca6573d3cbc018a8cff6ebcd53a181589b24f Mon Sep 17 00:00:00 2001
From: Paul Adenot <paul@paul.cx>
Date: Fri, 6 Nov 2026 10:19:13 +0100
Subject: [PATCH 2/2] Note that PeriodicWave imag[0] is also set to 0

---
 index.bs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/index.bs b/index.bs
index 30cdb7127..60d6dbfc3 100644
--- a/index.bs
+++ b/index.bs
@@ -9995,7 +9995,8 @@ Dictionary {{PeriodicWaveOptions}} Members</h5>
     ::
         The {{PeriodicWaveOptions/imag}} parameter represents an array of
         <code>sine</code> terms. The first element (index 0) does not
-        exist in the Fourier series.  The second element
+        exist in the Fourier series: it is set to 0 when the {{PeriodicWave}}
+        is constructed.  The second element
         (index 1) represents the fundamental frequency.  The
         third represents the first overtone and so on.