audio engineers PLEASE READ IMMEDIATELY

i need to know the answers to these questions by 3 pm (itll be almost 10 am when i post this)
i can't find anything on google, please help if you can



Simultaneous tones of 55Hz and 58Hz create how many beats per second? Why does this effect occur?

A 110 Hz tone with a level of -20 dB and other 11- Hz tone with a level of -20 dB in phase with the first tone are put into a mono audio track. Generally speaking, what happens?

If the sampling rate is 16kHz, what needs to be in the recording chain for a 12kHz tone to be properly recorded?

In the preceding question, if the needed link in the chain is missing, what happens to that 12kHz tone when it is recorded?




please.....thanks....

Just write '**** your shit questions' for each answer, then jack the course in and go and start a punk band or something...

Don't know if this is in time and I don't know the exact answers but here's some starting thoughts that you should be able to google or reference textbooks with?

This is more Physics than audio engineering although it's obviously relevant.

Simultaneous tones of 55Hz and 58Hz create how many beats per second? Why does this effect occur?

I think 3 per second, the difference between the two tones is 3hz (3bps). The beats are a variation in volume due to constructive and destructive superposition between the two tones.

This wikipedia article has some graphs and more detailed explanations in simple terms.

http://en.wikipedia.org/wiki/Beat_%28acoustics%29

A 110 Hz tone with a level of -20 dB and other 11- Hz tone with a level of -20 dB in phase with the first tone are put into a mono audio track. Generally speaking, what happens?

I think, if you read the article above, if the frequencies are further apart than 15-20hz (the tones in your example are 99hz apart) then the amplitude modulation of the beating is so fast that you don't hear the beats you hear another tone/frequency. In this case 99hz. You can try this out if you have Adobe Audition/Logic/Pro Tools etc, just generate 11hz & 110hz tones, put them on different tracks and see what you hear.

If the sampling rate is 16kHz, what needs to be in the recording chain for a 12kHz tone to be properly recorded?

In the preceding question, if the needed link in the chain is missing, what happens to that 12kHz tone when it is recorded?

This question seems to be getting at the Nyquist-Shannon sampling theorem and in particular aliasing.

Read this:
http://en.wikipedia.org/wiki/Nyquist%E2 ... ng_theorem

I think you need an anti-aliasing filter in the recording chain since Nyquist states that the sample rate should be at least twice that of the highest frequency recorded to avoid aliasing. Aliasing is artifacts (could be snaps, crackles, pops, noise etc) in the recording that were not present at the source.

16khz sample rate is obviously not twice the highest frequency of 12khz (needs to be 24khz minimum) so you will get artifacts if you don't use an anti-aliasing filter.

Again, you can hear what happens by generating a 12khz tone in an audio programme (Audition/Sound Forge etc) and then lowering the sample rate to 16khz. There will be digital noise.

Hope that helps, I definitely recommend that you read the articles I referenced and make sure the answers fit with what you remember being taught and that you're confident that they're correct. Do not copy and paste them verbatim (a simple google search by your lecturer or tutor may well bring up this very post). Then you'll have wasted my time because you won't get graded anyway!

So this is what school has devolved to.

answer=zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzy-your suspended!!!

it was a take home exam so i dont think there will be any trouble, we're allowed to look around online so asking people online is probably ok. these were the only questions on the test that i couldnt have researched to find the answer... so i dont think im doing anything wrong, but if i am, **** it, we never learned this shit anyway,

"allowed to look around online" is a bit different to copying out the questions and yelling PLEASE READ IMMEDIATELY to get people to do your exam for you

what makes you think you couldn't have researched to find the answers? if it's on wikipedia it's not exactly top secret information

shhh man, dont tell anyone about wikipedia

my bad. can I delete that post?

Wow, not so much as a thank you. I won't bother next time!

Paul_Caruso wrote:Wow, not so much as a thank you. I won't bother next time!

he's prolly waiting to see if the teacher marks those answers correct...

Paul_Caruso wrote:Wow, not so much as a thank you. I won't bother next time!

Lmao, damn.

Thank you Mr. Caruso.

mr_debauch wrote:

Paul_Caruso wrote:Wow, not so much as a thank you. I won't bother next time!

he's prolly waiting to see if the teacher marks those answers correct...

haha my bad i was about to but i got distracted by the dude saying im cheating and stuff and had to clarify that im not really cheating... but thanks good info it helped