So, I conclude from this discussion that the quality depends more on quantization levels than it does on sampling rate;
I don't like to say one is more than the other when two things are important. It's like saying the heart is more important than the liver for a person to live. Both are important for living, and both must work sufficiently well for good quality of life. Likewise, you need sufficient bitrate and sufficient quantization resolution. I think you understand the importance of both.
Could you please help me with
this query about bitrate?
The MPEG format is a compressed format, so it's not possible to extract quantization just from the bitrate.
I don't really get the overall point. Perhaps, you are saying that as quantization levels are increased, the noise increases. If possible, kindly elaborate a little. Thanks.
Yes and no. You are correct that quantization errors can be viewed as noise. But, my point was that you need to compare this quantization noise to other noise sources in your system. Thermal noise, shot noise and 1/f noise are examples of noise in a system. If these noise sources are creating variations much larger than the quantization resolution, it will be hard to hear (or see or measure) the quantization noise. That's all. Just make a common sense comparison. Why improve quantization resolution from 100 μV down to 10 μV, if you have a system with 100 mV of thermal noise?
In
post #4 you said, "First, the send and receive are just combined as one signal. Did you ever notice that you can hear yourself when you talk? People dont' usually talk at the same time, but if they do, their signals just add". Please don't mind my asking but are you sure that the signals get added up? What you say does
make sense but I'm just confirming because one can hear oneself back for several reasons.
You can hear yourself back for more than one reason, but clearly I'm talking about when you hear your voice from the microphone go onto the line and hear it back through the earpiece. Did you ever have a microphone on your side break? You hear the other person, but something doesn't sound right because your voice does not come through the speaker in your ear. Obviously, you hear your voice through the air and through the bones of your skull, but still the phone sounds not quite right. Then you hear the other person say, "hello? ... hello? ... are you there? .... ".
So, am I sure the signals add? That's kind of a strange question because I think we "assume" that they add. Based on long history and experience from many people over many years, we find that the principle of superposition works well in many cases. When people speak in the air, all the voices add up according to superposition. The separate acoustic waves seem to add nicely. On a telephone line, the two microphones are connected and drive the line, and the voltages seem to add nicely. Is it perfect addition? No, but it's a good assumption.
Different
types of interference can occur: destructive, constructive, intermediate, and
beat frequencies is just one of the possibilities. I think we can imagine an experiment here. Suppose, we have two telephone sets located some distance apart. Instead of two persons, we have two speakers connected with signal generators set to sine wave mode placed at mouthpieces and two sensitive microphones connected to oscilloscopes placed at respective earpieces. Suppose amplitude set on each signal generator is same. What will happen when both signals generators are in phase? Will the oscilloscopes show twice the amplitude? Will the displayed amplitude values be zero when signals generators are out of phase?
Yes of course. Signals can cancel or reinforce. You can also make two laser beams cancel out or reinforce with phase shifting. Still, two light bulbs don't usually create darkness.
I think the simple reason being that a **broken link removed** can do something similar to Fourier analysis and further it can synthesize related components into one signal.
Your guess is as good or better than mine. I really don't know too much about this. But, it seems reasonable that the human brain might very well be doing many approximate calculations that emulate real mathematical calculations. When we catch a ball, or throw one, we are mentally calculating trajectories as if our brains know Newton's laws and calculus. But, the details of what is actually being calculated is not something I can talk about with confidence.
I don't see why you consider a copper wire a waveguide. An EM waveguide is mostly a hollow structure and extends over short distances. An optical fiber is optic waveguide (not hollow). So, could you please let me the know the reason for using the term waveguide for a copper phone wire? Perhaps, you just used the term loosely.
First, I don't consider a copper wire to be a waveguide. I consider any transmission line to be one example of a waveguide. In special cases, a wire might make a reasonable transmission line, but it would need something else (a ground plane for example) to make it a transmission line. Two wires used in a highly controlled geometry makes a better transmission line.
There are people that don't like the terminology "waveguide" for transmission lines. So, if it's just a terminology issue, then substitute "transmission line" for waveguide in whatever I say. I consider them to be basically the same thing because i have done extensive calculations on RF, microwave and optical waveguides of various types. They all involve exactly the same physics (Maxwell's Equations) and mathematics.
Why doesn't a copper wire act like a good antenna at low frequencies?
Actually, didn't you already do calculations related to this before? At low frequency, the wire would need to be very very long, but that's ok. The same physics is at work, so it can act like a good antenna, with the right geometry.
A twisted pair cable and coaxial cable provide good shielding and they don't become good antennas at high frequencies but I think they also suffer from issues of impedance matching and imperfection points, don't they? In my view, line impedance and imperfection points are dependent upon the consistency and uniformity of the alloys used to manufacture these materials.
Yes, absolutely correct. But, I would tend to say that alloys are not the real issue. Consistency of geometry is more likely to be the issue nowadays.
I think you have this
arrangement in mind where you say "run two wires together".
Yes, I do. I was actually thinking of my old 300 Ohm TV twin cable that was popular for attaching to antennas before coax cable became more popular. But, that's exactly what it used to look like.
What do you really mean by "ground plane"?
Any, large area, flat conducting surface. It could be the earth ground itself, water, a large copper area on a circuit board, a wide area of chassis etc.
I don't see what bending and perturbations along the length have to do with coupling losses. Because coupling loss also known as connection loss is the loss that occurs when energy is transferred from one circuit, circuit element, or medium to another. Perhaps, what happens is that bending and perturbations along the length cause the signal leak out into air or surrounding space to great quantity.
That last sentence is correct, but that is an example of coupling losses. Basically, guided modes become coupled to backward guided modes for reflections, or to forward radiating modes for scattering loss. Don't worry about this terminology as it would not make much sense until you get into detailed design/analysis of waveguides/transmission lines. Then, you would get into mode-coupling theory.
