Chapter 17 Flashcards
The speed of sound depends on the properties of the medium; in general it is slowest in
gases, faster in fluids, and fastest in solids.
The speed of sound depends on the properties of the medium; in general it is slowest in
gases, faster in fluids, and fastest in solids.
The speed of sound depends on, amongst other things like what? and its equation
the temperature (especially for gases).
Volume: This is related to the
intensity of the sound wave
Pitch: This is related to the
the frequency.
Audible region: approximately 20 Hz to 20,000 Hz; upper limit decreases with age
→ Infra sound: below 20 Hz
→ Ultra sound: above 20,000 Hz
The relationship between sound level and intensity is logarithmic:
Intensity of sound relates to what?
Decibels
* Decibels give us a measure for how loud sound is perceived.
A sound that is perceived as twice as loud corresponds to an increase of
10 dB. But this corresponds to an increase in the intensity of the wave (as measured in 𝑾 𝒎^(−𝟐)) by a factor of TEN!
Intensity
The Doppler effect
is an observed change in frequency and occurs when a source of sound moves relative to an observer.
What happens between a fire truck as it moves towards/away from a person? explain using the doppler effect
If a source moves towards an observer that observer will observe a higher frequency / shorter wavelength; the opposite is true if the source is moving away from the observer.
Doppler equation :
- Vsound: speed of sound
- Vobs: speed of observer
- Vsource: speed of source
+ when sources are moving towards each other
-when moving away from each other
Beats
- If we add together two sinusoidal waves of slightly different frequency, we obtain a phenomenon known as “beats”.
- The two waves (of slightly different frequency) add together in such a way that sometimes they add constructively and sometimes they add destructively.
Sources of sound: Vibrating Air Columns
open and open-closed
- Open-Open: these pipes (or instruments) have both ends open to the atmosphere
- Open-Closed: these pipes (or instruments) have both one end closed and one end open to the atmosphere
node and anti-node diagram (fixed at both ends)
open-open air columns (in the first harmonic) have antinodes at both
ends and a node in the middle
Different harmonic for open columns
What is all the equations required for harmonics
What is all the equations required for harmonics
Sources of sound: Summary of instruments (stringed, open and opne-closed)
