Wave Theory Flashcards
Wavelength formula
Velocity/Frequency
Velocity
Feet per second
Frequency
Cycles per second, Hz
Velocity for sound at room temperature?
1130 feet per second
Rounding to 1000 is typically acceptable
Period or Time formula
1/Frequency
1=cycles PER SEC
1000/Frequency
1000=cycles PER MS
What is the wavelength of 1kHz in feet? Use 1000 instead of 1130.
V/F
1000/1000Hz = 1ft
What is the wavelength of 500Hz in feet? Use 1000 instead of 1130.
V/F
1000/500Hz = 2ft
What is the wavelength of 2000Hz in feet? Use 1000 instead of 1130.
V/F
1000/2000Hz = 0.5ft
Multiple arrivals at 0° phase
Complete addition
Multiple arrivals at 90° phase
Partial addition
Multiple arrivals at 120° phase
No addition
Multiple arrivals at 180° phase
Complete cancellation
Boundary Reflections
1ms time offest between the first and reflected sound causes comb filtering with 1kHz frequency spacing at the listening position
ex. direct path = 50ms, reflected path = 51ms
Speaker interactions, overlap in speaker coverage
1ms time offset between the two speakers causes comb filtering with 1kHz frequency spacing at the listening position
ex. upper speaker path = 51ms, lower speaker path = 50ms
Microphone interaction, inaccurate placement of 2 mics
1ms time offset between two mic positions causes comb filtering when the mics are summer together in the mixing console
ex. Mic 1 path = 5ms, Mic 2 path = 6ms
Direct and microphone signal interaction, latency differences between mic and DI sources
1ms time offset between two direct and mic’d signals causes comb filtering when the channels are summed together in the mixing console
ex. Mic path = 1ms, Direct input path = 0ms
Why is it called comb filtering?
Because the frequencies are being cancelled out in intervals, causing the waveform to create spikes going up and down, resembling teeth of a comb
Polarity vs Phase
Polarity is about + and - of the waveforms, and phase is about time
2 speakers in polarity and in phase
Both speakers matched polarity +- and are both reaching the listener at the same time
ex.
1st speaker = +-, 1ms
2nd speaker = +-, 1ms
2 speakers in polarity yet out of phase
Both speakers matched polarity, but are not reaching the listener at the same time
ex.
1st speaker = +-, 1ms
2nd speaker = +-, 2ms
2 speakers out of polarity yet in phase
Speakers are not matching in polarity, but are both reaching the listener at the same time
ex.
1st speaker = +-, 2ms
2nd speaker = -+, 2ms
2 speakers out of polarity and out of phase
Speakers are not matching in polarity and are not reaching the listener at the same time
ex.
1st speaker = +-, 1ms
2nd speaker = -+, 2ms
Latency in cabling, explain
0 latency. Force applied through the cable causing what is going in at the start of the cable to push out what’s built up at the end of the cable. An example would be a pipe full of BBs, if you push in one, it’ll cause one to fall out the other end. The force of pushing is voltage, and the BBs are electrons.
Does the length of a cable affect latency?
No, because voltage pushing electrons in a cable causes electrons to come out the end the moment one enters the start. There’s no delay at all.
