calculate rate of alias

[xander123]

Hi all,

i have a question about to calculate the rate of alias with a given sample frequency. for example fs = 8000Hz, 1/2fs = 4000Hz
If i want a 3 times of alias rate what is my frequency? The same for 6 times the rate of alias?

Could someone help me?

[garageband]

How is this information useful?

[bozmillar]

alias rate? I'm not sure those two words together mean anything. I'm seriously interested in what you are asking, it's just that the question doesn't make sense.

[xander123]

my sampling frequency is 8000Hz. i have to find the frequency where i can get 5 times alias.

so i know that my nyquist/alias is 4000Hz.

does this mean my answer is 3 times my sampling frequency?

[garageband]

my sampling frequency is 8000Hz. i have to find the frequency where i can get 5 times alias.

so i know that my nyquist/alias is 4000Hz.

does this mean my answer is 3 times my sampling frequency?

This just sounds like jibberish to me. I would like it if you could elucidate what you are up to.

[bozmillar]

my sampling frequency is 8000Hz. i have to find the frequency where i can get 5 times alias.

so i know that my nyquist/alias is 4000Hz.

does this mean my answer is 3 times my sampling frequency?

Is this a school problem? I have no issues helping out, but "5x alias" doesn't mean anything as far as I'm aware. I've never heard of aliasing referred to as a rate. either there is a language barrier here, or an understanding of aliasing barrier. If this is a school problem, it might be better just to ask the way it's written.

[Stan_Halen]

I don't get it either. Alias to my way of thinking is not something you want or can control, although I believe digital converters do add Alias to a signal - basically "noise" to offset other nasties of conversion. Similar to Tape Bias used on Analog equipment if I'm not mistaken. It is something that electrical engineers have to contend with when building audio interfaces, but not something us Joe Blow's spend much time thinking about. If you must really get your head around it this may help:

Aliasing - Wikipedia, the free encyclopedia

[bozmillar]

aliasing can and should be controlled. It's also very easy to calculate what the aliasing artifacts will be from a given signal with a given sample rate. It's just that in the context of the question, "5x alias" doesn't make any sense.

It's like saying "I have a quarter gallon cup and I need 5x milk froth. What do I need?"

[brandondrury]

I'm glad everyone else is baffled, too, because I'm having trouble with the question as well.

[m24p]

It sounds like you're trying to do undersampling?

I'm not sure why, though.