AEC3: Correcting minimum comfort noise levels

This CL corrects the minimum bound for the estimated
comfort noise level.

Bug: webrtc:10533
Change-Id: I473275ffbc7bb52572315849f30e13b764109d92
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/132003
Reviewed-by: Per Åhgren <peah@webrtc.org>
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27567}
diff --git a/modules/audio_processing/aec3/comfort_noise_generator.cc b/modules/audio_processing/aec3/comfort_noise_generator.cc
index 1e3cdf2..bedd227 100644
--- a/modules/audio_processing/aec3/comfort_noise_generator.cc
+++ b/modules/audio_processing/aec3/comfort_noise_generator.cc
@@ -139,8 +139,9 @@
     }
   }
 
-  // Limit the noise to a floor of -96 dBFS.
-  constexpr float kNoiseFloor = 440.f;
+  // Limit the noise to a floor matching a WGN input of -96 dBFS.
+  constexpr float kNoiseFloor = 17.1267f;
+
   for (auto& n : N2_) {
     n = std::max(n, kNoiseFloor);
   }