# Why does a sound of two sources of same-amplitude come out louder than one-source sound with the same amplitude?

Sorry if the question is stupid. The last time I touched physics was in school and I have never come back to it since. But this question popped up just recently in my life and I realized I don't know how to answer it.

As far as I remember, the amplitude of a sound wave defines the loudness of the sound - the bigger the amplitude is, the louder is the sound.

And I also remember that the frequency of a sound wave defines its pitch - the faster is the oscillation, the higher is the sound pitch.

Now imagine we take two oboes, each one playing the same note and with the same level of loudness. Both are producing a sound with the same amplitude. This means that the loudness of the resulting sound of two oboes will still be the same, but in the reality two oboes will sound louder than one. Why is it so?

• The reason two oboes do not cancel each other out is not just because the players (or instruments) do not generate the exact same sound, but it also depends on the distance between them. Their distance has to account for phase offset of $\pi$ (or $180^{o}$) in all frequencies for the waves to cancel out. This is impossible in practice and this is why they never cancel out. A "statistical" treatment of the two sounds would lead to an increase in their level of about $3 dB$ which corresponds to their energy being summed. As Belal Bahaa mentioned sound-cancelling headphones use this (cont.) Aug 25, 2022 at 12:03