Digital Signal Processing Oct 7/9

Question 1

What are the challenges of analog signals?

Answer 1

Analog signals are continuous
- a value is possible for every possible time point to infinity

This makes it difficult to store, access, and analyze the data
- analyzing analog data can be painfully slow
- to take advantage of modern computing systems we must digitize them.

Question 2

What is Analog-to-digital conversion?

Answer 2

• It is the process of transforming analog data into the digital format.
• The process involves sampling; it keeps some values and dumps the rest.

Question 3

What rule does sampling rate set?

Answer 3

It determines how many values (samples) are kept per second interval.
- if we pick 100 samples from a one-second long interval our sampling rate is 100hz.

Question 4

What is the default sampling rate?

Answer 4

44,100hz

Question 5

What is Nyquist’s theorem?

Answer 5

“The Nyquist theorem specifies that a sinusoidal function in time or distance can be regenerated with no loss of information as long as it is sampled at a frequency greater than or equal to twice per cycle.”

Question 6

How is sampling rate correlated to the Nyquist theorem? What is sampling rate?

Answer 6

Sampling rate must be double than the frequency we want to capture for no loss of information, this is the basis of the theorem.

2 samples within one period (cycle) of the wave.

Question 7

What is Nyquist Frequency? How is it different from sampling rate?

Answer 7

Your Nyquist frequency is just the highest frequency you want to record. In order to get that frequency you need a sampling rate that is double that amount.

eg. We want to record 100hz (we want 2 samples per period)
Sampling rate - 200hz
Nyquist frequency - 100hz

Question 8

What happens when you sample at a rate lower than the Nyquist frequency?

Answer 8

aliasing - higher frequencies will show as low.

Question 9

What bit is enough for acoustic analysis?

Answer 9

16 bit.

Question 10

How do you get rid of quantization noise?

Answer 10

There will always be a bit of quantization noise, however if there is still too much you will have to raise the bit depth.

Question 11

What is the Fourier transform?

Answer 11

Named after Jean Baptiste Fourier, french mathematician, it is the mathematical analysis of a complex wave into its component frequencies.

Question 12

What does sine have to do with the sin wave?

Answer 12

• When the sine of an angle is plotted against that angle measure, the result is a classic “sine curve” shape,