Why are do some notes sound louder than others? Harmonics?

Question

In a room, some musical notes played with the same volume seem louder than others. Is it due to harmonic vibrations within the room or within my ear?

Answer 1

Could be either.  The frequency response of the human ear is not flat.  Also, at certain frequencies, the room may 'sustain' certain notes and not others.

Answer 2

Harmonics can definitely affect the loudness of various notes due to the mathematical relationship between a note's wavelength and a rooms dimensions.

Your position in the room can also make a big difference.  Like waves in a pond, sound will bounce around a room and when they collide the may add together making taller waves or deeper troughs or they may cancel each other altogether.  As you move around a room, different notes will sound louder in different locations.  Moving the speakers around the room will also change the apparent volume of different notes.

Your speakers can also affect how loud different notes are.  Some speakers are better with high frequencies (treble).  Others are better with low frequencies (bass).  Still others are are best in the middle or mid-range frequencies.  Even very expensive speakers seldom produce all frequencies equally.

Also, speakers produce frequencies with varying efficiency at varying volumes.  At low volume a speaker could produce bass more efficiently than treble.  At high volumes the same speaker could produce treble more efficiently than bass.

Your amplifier is another variable.  Amplifiers also vary in performance, but not quite as noticeably as speakers.

Finally, it's possible that you could hear some resonant vibrations within your ears themselves, but typically the sound would have to be very loud. In fact, hearing loss could also affect how loud different notes appear to be.

Room resonance, speaker performance, speaker placement and the health of your ears all affect how loud notes appear to sound at the same volume.