L2. analogue & digital signals

Question 1

What are the frequency-components of a signal?

Answer 1

SUM of many sine & cosine waves of different FREQUENCIES

Question 2

When will you not lose any information about the original wave after sampling?

Answer 2

When signal has no frequency components above Fhz and you use a sampling rate Fs > 2*F

Question 3

If we sample component of frequency F where F > Fs/2 what will it’s sampled frequency be?

Answer 3

F = Fs-F

Question 4

What is the restulr of Dynamic Range compression on cds?

Answer 4

Make quiter parts louder

Question 5

What is the dynamic range of human hearing in DB?

Answer 5

120dB

Question 6

To express an SPL (Pa) in dB what ratio is used?

Answer 6

SPL at ears/ 20 μPa (quietest audible)

Question 7

In telephony what is Fs, bits/sample and bit-rate?

Answer 7

8kHz
8 bits/sample
8x8 = 64 kbit/s

Question 8

What does each binary number represent in uniform quantisation?

Answer 8

Voltage level

Question 9

Max SQNR achieveable when m-bit uniform quanitzer applied to sinusoidal wave?

Answer 9

6dB*M + 1.8

Question 10

How does Linear Predictive speech Coding work?

Answer 10

A.Sender derives 50 parameters/sec
1. digital filter coefficients (VOACAL TRACT)
2.loudness
3.voiced or unvoiced
4.(if voiced) Fundamental frequency
B. Send to receiver
C.Reconstruct speech