Sound waves is a form of energy that can be measure my Hertz (a frequency measure).

What happens wen two sounds were produced at the same time. Lets say one at 440hz and the other at 220hz. What is the resulting sound in hertz?

Thank you. Being an engineer, you have given a scientific answer. Unfortunately, I do not have a good background in science. I only understood
I am specifically looking at it from a music point of view. I am trying to get the computer to play a tune by sending a certain frequency to the speaker. For example, the note Do (261.626hz) and the note Re (293.665hz) were to be played simultaneously, what is the resulting frequency?

Good example. Comparing one with another twice as fast. 20hz move 1 cycle while 10hz only move half.

Given that you did tA + tB, "Interpolate" is also the same as saying "horizontal summation"?

You are giving me an answer in magnitude measure by dBa (as written by your y axis). I was looking for an answer in hertz.

I guess if you sum f(A) and f(b) horizontally you will get another function say f(d) which I think you plotted two points (one point being an estimate). As it is, I should be able to obtain f(d) and eventually work out how many hertz, right?

This dBa which I guess is a measure of volume? While I can understand volume = 0 (meaning no noise), I am not sure what negative volume means.

Do they really ossilate up and down the zero?

This post has been edited by faceless: Sep 15 2010, 12:10 PM

Horizontal Summation
I am not sure where I got this term from. School had been ages ago. It is most likely from math. Since a practising engineer have not heard such term before then lets just say I learnt math from the eskimos.

Let me see if it is the same as interpolating. We will take an easier example. Graph 1 is y = x^2 (^ means to the power of in this case y=x squared). Graph 2 is y = 50. If you interpolate both the graphs would you get y = x^2 + 50?

Now can you tell me given a frequency and magnitute how do I get the above graphs?

Then tell me how to a get an ideallised motion?

As I mentioned previously, I was trying to apply it to music. You play two or more notes simultaneously its call a chord. Electronic keyboard seems to be able to do this just fine. I am sure there is a way. It comes down to - do we know how or not.

Thanks for your input, Awakened.

Thanks Befitozi,
As long as the answer is in term of hertz, it is the answer that I seek. I am not able to see the pictures/applets. Reading the text, I gather that it is actually looking for the area between the graphs since intergal calculas was used.

I have not heard of the frequency sprectrum. I just look it up on wikipedia. It just apply the light spectrum (a form of wave) to sound (another form of wave). It also give me links to look up the math I did not learn (like Fourier Transformation).

Looks like more reading for me. When all is done, I wonder if I could get vb (the programming I use to do this project) to do integrate a cosine wave.

Awakened,
Dont feel so bad and apologetic. The graphs you done at the beginning had put the science in a math form. In that from presentation, it had help me undertand the concept of sound waves much better.

Heavy math stuff is not a problem. No matter how a number is transformed into another number it can usually be traced back to plus and minus. From there you go to divide and multiply and subsequently to exponentials ... Heavy science stuff is a problem because I did not go to science streem. I lack the knowledge of the fundamentals to move from concept A to Concept Z.

I have done some homework and I am stuck.

These stuff are base on the second link Befitozi provided
A pure tone can be written as a cosinusoidal signal of amplitude , frequency , and phase angle. Frequency in units of radians/second, with t in seconds, and the phase angle to be in radians.

An alternative is to express the frequency in units of Hertz, abbreviated Hz, given by f1 = Freq/2pi

I think this 2pi is a radian measure. Convert to degree it should be 180 degrees?

In the Fourier series these frequecies are added up. The result is a list of constants that add up to a bigger constant. I wonder about appllying intregration to it.

I think I get this. Circumference is 2 x pi x radius. Since the largest sin or cos value is 1, the radius must be 1 (that much I gathered from a doing math revision recently through online tutorials). Thus it becomes 2pi. Tell me if I am correct?

I am not sure I get this part correctly. Let me tell you my simplistic view about it. From the given link, tone = Amplitude x cos(frequency in radian + phase angle in radians). If the whole thing is express as Hertz then it may be as simple as say 440/2pi hertz. Lets say the entire thing in bold is written as X. In a Fourier series I can write x(t) = x1+x2+x3+...+xn. Then again x can also be written as k/2pi (a constant). Thus adding the string of x is also a constant.

I am not commenting on you third paragraph. I think I need to understand the second paragraph first. I am not dealing with mp3. I am sending a frequency to the computer speaker to play a sound. It does not require sound card. I think mp3 stuff needs a sound card.


Drian, I dont get what you are trying to say.

This post has been edited by faceless: Oct 6 2010, 09:31 AM

Thanks Drain,
I beleive Awakend covered what you have said in the earlier parts of this thread. In summary it was basically like - at times 400Hz will drown out out the sound of 220Hz and at other times the other way around.

For that I pose you the same question. What is the frequency chosen by eletronic keyboards manufacturers when more than one note is pressed?

There is no resultant frequency only if the by product is not a sin or cos wave. If the by product, like through convolution, give another sine wave there is a frequency. That so far had been my understandng base on material given to me here. Are you telling me the resultant is not a sine or cos wave?

Thanks for the link Drian,

I did come across another link that simply say take the average of both frequency as the resultant frequency. I extracted part of it and paste it here. I have also included the link if you want to read the entire passage. What are your comments.


For example, if you add a wave oscillating at 445 Hz with one that is at 450 Hz, the resulting frequency will be an average of the sum of the two waves: (445 Hz + 450 Hz)/2 = 447.5 Hz. This waveform is close to a sine wave, since the frequencies are almost the same.
The amplitude of volume of this combination will oscillate at the beat frequency of the difference between the two: (450 Hz - 445 Hz) = 5 Hz.
Now, if you add 440 Hz and 500 Hz notes, the resulting waveform will be a complex version of a sine wave and will sound like a blurred or fuzzy average of the two tones. The average frequency of this complex wave will be (440 Hz + 500 Hz)/2 = 470 Hz.
Also, its beat frequency will be 60 Hz, which would sound like a very low-pitched hum instead of a fluctuating volume.

http://www.school-for-champions.com/science/sound_beat.htm

Befitozi & Awakened, I appreciated your comments too.