diff --git a/index.bs b/index.bs
index 0b34e1e06..5e26a227b 100644
--- a/index.bs
+++ b/index.bs
@@ -1054,8 +1054,8 @@ Methods
bufferSize: The {{ScriptProcessorNode/bufferSize}} parameter determines the buffer size in units of sample-frames. If it's not passed in, or if the value is 0, then the implementation will choose the best buffer size for the given environment, which will be constant power of 2 throughout the lifetime of the node. Otherwise if the author explicitly specifies the bufferSize, it MUST be one of the following values: 256, 512, 1024, 2048, 4096, 8192, 16384. This value controls how frequently the {{ScriptProcessorNode/onaudioprocess}} event is dispatched and how many sample-frames need to be processed each call. Lower values for {{ScriptProcessorNode/bufferSize}} will result in a lower (better) latency. Higher values will be necessary to avoid audio breakup and glitches. It is recommended for authors to not specify this buffer size and allow the implementation to pick a good buffer size to balance between latency and audio quality. If the value of this parameter is not one of the allowed power-of-2 values listed above, an {{IndexSizeError}} MUST be thrown.
- numberOfInputChannels: This parameter determines the number of channels for this node's input. Values of up to 32 must be supported. A {{NotSupportedError}} must be thrown if the number of channels is not supported.
- numberOfOutputChannels: This parameter determines the number of channels for this node's output. Values of up to 32 must be supported. A {{NotSupportedError}} must be thrown if the number of channels is not supported.
+ numberOfInputChannels: This parameter determines the number of channels for this node's input. The default value is 2. Values of up to 32 must be supported. A {{NotSupportedError}} must be thrown if the number of channels is not supported.
+ numberOfOutputChannels: This parameter determines the number of channels for this node's output. The default value is 2. Values of up to 32 must be supported. A {{NotSupportedError}} must be thrown if the number of channels is not supported.