1) Decibels measure the ...

a) Signal strength above zero power (no signal at all)

b) Signal energy per square meter

c) Signal power per square meter

d) Signal strength relative to the lowest detectable power

2) Period - 0.5min. Speed - 200km/h. What is the frequency?

a) 400Hz

b) 100Hz

c) 2Hz

d) 0.033Hz

3) What is the speed of sound at 45 degrees C?

a) 359m/s

b) 359km/h

c) 331m/s

d) Mach 0.7

4) Destructive interference results in

a) Lower amplitude

b) Lower frequency

c) Lower amplitude and frequency

d) Lower amplitude but higher frequency

Please answer ASAP

Thanks