An elementary study of 440Hz sinewave radiation from various surface materials

440Hz means by definition 440 repetitions of a periodic phenomenon in one second.


[When a 440Hz tuning fork is struck it vibrates and we humans can hear the pitch of the musical note A4 when sound pressure level intensity is low enough.
If intensity is higher our brain perceives progressively a note lower than A4 [Stevens] (towards bA4 or A4 flat).
Pitch (what our brain perceives as height of tone) depends not only on frequency but on intensity too.]


When a tuning fork is held by our hand and struck to vibration we hear a very faint sound at say 2 feet.


This is because the vibrating metal prongs have such small surface area making relatively few air molecules to vibrate. So little sound comes to our ears. Same with an electric guitar thin vibrating string (electric guitars do not have a vibrating soundboard surface).


When we touch the base of a vibrating tuning fork to say a table, a guitar soundboard, floor, wall etc sound intensity multiplies many many times. This is because a large vibrating surface sets into vibration say trillions trillions of air molecules.


Here are some elementary observations when the base of a vibrating tuning fork touches surface areas of different materials:


Linoleum 1m x 2m carpet standing on wooden floor:
Amazing sound, loud with no overtones. There is body or volume. Sounds like a very pure sinewave.


Linoleum part of above carpet standing one foot above wooden floor and tuning fork placed on such hand lifted area:
Same as above.


Wooden floor:
Sound is loud but with not much volume in the sense of body to sound. It sounds thiner than linoleum. There is high frequency content which is strange for a sinewave. So it must be overtones of the tuning fork. Or harmonic production or distortion from wooden floor.


Plastic back of chair.
Similar to linoleum but of worse sound quality.


Metal feet of table.
Somewhat metallic sound with overtones?


The best sound quality of a pure sinewave nature was undoubtedly from the vibrating linoleum.


See also: Increase of loudspeaker bass radiation by transmitting vibration to linoleum with no observable sound coloring artifacts in other euroelectron posts.


Reference:


Sound and Hearing - S. S. Stevens, Fred Warshofsky - Chapter 4: The Mind's Influence - Life Science Series