Flashcards
Acoustics Term 3
Cards in this deck (28)
- 1What is speaker boundary interference-deviations in speakers perceived frequency response due to interference by close proximity boundary reflections
-only occurs with lf - 2How much output occurs when a speaker is placed at a node, how about an antinode0 output = node
Max output = antinode - 3How much db gain when speakers are place by a: -wall -two walls (corner) -three walls (floor of corner)-wall = 3 db increase
-two walls = 6 db increase
-three walls = 9 db increase - 4What should you do with large speakers-flush mount them to prevent reflections from boundaries
- 5What two things does the proximity of speakers to walls or corners directly effect in terms of acoustic distortion-speaker boundary interference response
-coupling of room modes - 6What is comb filtering-when the direct and reflected signals combine and cause an interference
- 7How do you determine the starting frequency where comb filtering occurs-spacing in between peaks or nulls divided by 2
- 8Is comb filtering an issue in large rooms-no it is only an issue in small rooms
- 9What is the critical distance-area between the sound source to the point where the amplitude of the direct sound is equal to the amplitude of the reflections
- 10As RT60 increases...-critical distance decreases
-more reflected energy = less direct energy - 11What are the three main equations used to calculate rooms-sabine equation
-eyring equation
-fitzroy equation - 12Why use the sabine equation and what do you have to take into account-it's simple
-accurate in average rooms
-assumes low absorption
-assumes amount of reflection/absorption is equal - 13Why use the eyring equation and what do you have to take into account-improved accuracy over the sabine equation
-accurate for rooms containing high absorption - 14Why use the fitzroy equation and what do you have to take into account-improved accuracy over sabine and eyring
-used when amount of absorption/reflection is unevenly distributed
-accurate for long or narrow rooms - 15All acoustic analysis is based on working with what three things-frequency
-amplitude
-time - 16What are the three most common test signals-MLS (white noise)
-pink noise
-swept sine (chirp) - 17What is MLS-maximum length sequence
-is a digitally generated white noise burst
-works well in noisy environments - 18What is a swept sine (chirp)-a sine wave that quickly sweeps through entire frequency range
-susceptible to noise colouration
-very accurate - 19What does a spectrogram display-displays LF amplitude over time
-basically a waterfall plot viewed from the top - 20What does a LFETC display-displays LF amplitude over time in 3D
- 21What does a LF response graph display-displays LF over multiple user defined time slices
-used to examine LF behaviour in a room - 22What does a RTA do-a real time analyzer displays spontaneous amplitude and frequencies at a given location in real time
- 23Whats the problem with using gate curves/windowing when examining lf-lf has long wavelengths so they require a long gate time usually at least 50 ms
- 24What does an impulse response graph display-displays energy over time
-used to determine if measurement was performed correctly - 25What does a linear frequency response graph display-displays frequency and amplitude
-used to examine the effects of comb filtering - 26What does a logarithmic frequency response chart display-displays frequency on a logarithmic scale and amplitude
-allows for the examination of actual perceived frequency response at mix position due to comb filters - 27What does an ETC display-displays energy over time of user defined freq bandwidths from 500hz to 8khz
-used to compare arrival time, level and frequency response of reflected signals to the direct signal - 28What does a schroeder plot do-is used to separate the decay from the noise floor
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- Flashcards on Acoustics Term 3, created by Alex Meulenbeld on 05/02/2017.
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- Alex Meulenbeld
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