Discussion»Questions»Science and Technology» In order to qualify as "sound" there must be a source. There must also be a receiver, right? Sound cannot exist alone on its own can it?
Is the following correct? In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-, and gamma rays.
Being as EMR includes radios waves, is the conversion, by the receivers, much different than what the brain does to the vibration waves that we convert to sound?
The vibrations of the eardrums are converted to electrical signals the travel to the brain to create what we call sound. This is an oversimplification due to my lack of knowledge of the human body. Radio signal are converted differently through a series of electronic components, such as diodes and capacitors etc. Here is a very simple one.
With RF propagation the "intelligence" has to be superimposed on the signal at the transmit end and stripped off at the receive end. We call that process modulation and demodulation. It comes in two flavors: amplitude modulation where the actual level/power of the RF signal is instantaneously varied by the information being sent, and frequency modulation where the actual frequency of the signal is instantaneously varied by the information being sent.
That's the old "Tree in a forest" question. By definition sound is the physical vibration of a medium, be it solid, liquid or gas. So it can exist without a receiver.
I asked another question specifically about that. If people rant and rave and no one pays any attention do they make a sound? A physical vibration can exist but if there is no receiver how is it perceived Ele? It isn't except by some mechanical device that registers it rather like earthquakes are registered by machine. Of course we FEEL the effect of them. Some sounds are above/beyond our ability to hear. Dog whistles are often used as an example. Dogs can hear them but humans can't. So they are essentially soundless as far as we are concerned. But since dogs hear them there is a receiver. I don't know. Some things boggle my mind. Sound is one of them. Thank you for your reply! :)
This post was edited by RosieG at October 3, 2017 7:38 AM MDT
No one . I mean can inanimate objects "hear" anything? I know about The Big Boom. But all there was were masses of matter, none of which had auditory ability. Animals can hear so I suppose microbes can too. I'm gonna ask that question. Thank you for trying to help me out here. I'm have to keep working on this. :)
Sound is a word that has multiple meanings so it depends . . .
In the realm of the physical sciences sound is a mechanical vibration (as opposed to the propagation of an electrical waveform) that typically, but not always, propagates as an audible wave of pressure, through a transmission medium such as a gas, liquid or solid. The presence of the mechanical vibration makes for the sound, no "receiver" necessary. It has practical applications too. There's such a thing as a SAW filter in electronics. The acronym SAW stands for Surface Acoustic Wave, the link to sound being that little Acoustic part. (Yes, there is a transducer to generate the mechanical vibrations and one to "receive" them in this case.) Those filters usually operate well above the range of hearing for most creatures with that capability.
In the realm of human physiology and psychology, sound is considered to be the actual reception of such waves and their perception by the brain. But I do tend to question that definition because as an example if you have two people in a room, one stone deaf, and there is a sound introduced into that room there's still sound present even though one of those two people is incapable of actually hearing, or "receiving" it (the hearing person being a "control" to verify the actual presence of the sound). And then there's Beethoven who was stone-cold deaf towards the end of his career and he still managed to "hear" his own music as he composed it.
Anyhow, humans can hear sound waves with frequencies between roughly about 20 Hz to roughly about 20 kHz. Sound above 20 kHz is considered to be "ultrasonic" and below 20 Hz is considered to be "infrasonic". Other animals have different hearing ranges. for some strange reason with certain pets the hearing ability seems to be "peaked" at around the range of the sounds made by a common electric can opener while in operation.
Benedict Arnold 