Acoustics Flashcards
What is sound?
- Sound is produced by a series of compressions and rarefactions which are converted into signals by pressure sensors in your ears, allowing your brain to interpret them as sound.
- The interpretation depends on the rapidity and magnitude of the compressions/rarefactions.
- When you speak, you are only producing areas of low and high pressure.
What is fourier analysis?
Fourier analysis shows us which different frequencies are in complex sounds, allowing us to try and block these frequencies in our building design.
What is the equation for frequency?
What is the equation for pressure?
Units = Pascals (Pa)
What are complex sounds?
Complex sounds are made up of a range of different waves, producing a number of different frequencies.
What is the unit of intensity?
- Watts per m2
- W/m2
What is the unit of sound power?
- Watts
- W
What is the equation for sound pressure level (SPL)?
What is the equation for sound power level (SWL)?
What are the units for SPL and SWL?
If you see the word level, you know the units are decibels (dB).
What is the difference between sound pressure and sound power?
- Sound pressure is what you experience.
- Sound power is what the source outputs.
What happens when you add multiple sources?
- When adding a source, we add 3dB to the total SPL/SWL.
- However, if one source has an SPL/SWL 10dB than another, it dominates and we ignore the weaker sound.
What is the equation for the total SPL of multiple sources?
What is the equation for sound power at a location if you have a known sound power output?
What is the equation for sound pressure level at a location if you have a known sound power level?
What is the equation for sound power at a location if you know the sound power at another location?
How do you adjust sound pressures?
“Adjust a sound pressure level of 56dB at 63Hz for the sensitivity of the human ear, giving your answer in dB(A)”
- At 63Hz, the A-weighting is -26.
- so… 56dB - 26dB = 30dB(A)
