Audio Systems: the mistery of sound, flat frequency response, room resonances

Question
Hi I did a sine test in my room and notice that some of the frequencys from 20hz-20,000hz where much louder than others like 50HZ over 70hz or 1000hz over 2000hz and all equipment was at bypass processing mode to much sure sound was flat so what is the I guess science to these overtones Thanks!!!

Answer
Overtones are harmonics and that would indicate distortion which comes from overdrive.   Perhaps you used the wrong term.

What instrument did you use to measure the sound level vs frequency?  If you are using just your ears that means virtually nothing because the human ear is a very, very lousy test instrument!

Producing sine wave tones in a typical resident home room have many factors that will cause variations in sound pressure level.

ONE:  Loudspeakers are never very flat in their response; rather they wander all over the place due to their irregularity in response and their polar pattern which loads into the room in various ways over the frequency range. The crossover network in the speaker system causes certain anomolies that cause further variations.

TWO:  The room itself has its own resonance and absorption characteristics that will effect the pressure level.

THREE:  The room dimensions give rise to bass resonances and wavelength variations that result from these geometric conditions.

Conclusion:  The amplifier can produce a very flat frequency response but the speakers, the room and your ears are far, far from a flat response.  This is why audiophiles spend thousands of dollars in pursuit of the equipment which, to their ears, provide the best compromises in search of the great sound they are looking for.

Let me know if there are further questions.
C

PS:  The 50 to 70 Hz region is where speakers and room resonances notoriously effect sound reproduction.  1kHz to 3Khz is an area of speaker crossover and narrowing of the radiation pattern of most speakers start giving serious uniformity problems. Further where the measurements are taken within the room (where the microphone is placed or where the listener is standing) will make a huge difference.