What is considered bad acoustic reflection in milliseconds?

A bad acoustic reflection refers to the delay at which sound reflections become perceptible and can interfere with the clarity of the main sound signal. In general, reflections that occur in less than 10 milliseconds are considered problematic because they can interfere with the direct sound reaching the listener, leading to a phenomenon known as comb filtering. Comb filtering occurs when sound waves interact, resulting in fluctuating frequencies that can severely affect audio quality. Therefore, a threshold of less than 10 milliseconds is typically established; anything below this value is likely to create an adverse acoustic environment, impacting the intelligibility of speech and the overall listening experience.

Reflections occurring after this period (greater than 10 milliseconds) are usually less detrimental, as they are likely to be perceived as echoes rather than interfering sound. Thus, while many might consider a range of reflections, research and acoustic studies emphasize that the critical threshold is indeed around 10 milliseconds for acceptable sound quality in most environments.