Wk1 Flashcards
Three Components of a Sound Network
Emitter/source
Medium (gas, liquid, solid)
Receiver/Receptor (ears, microphone)
Mechanical Wave
A disturbance or variation that travels through a medium
Requires a medium to travel through, not capable of transmitting in a vacuum
The density of the medium dictates how far the sound travels
Sound is a mechanical wave
Speed of sound
340-350mp/s
How is sound produced
Sound is produced by a vibrating source, it vibrates molecules that vibrate ones adjacent to them
This causes regions of higher and lower pressure (compression and rarefaction)
Compression and Rarefaction difference
Compression - areas of higher pressure
Rarefaction - areas of lower pressure
Types of Mechanical Waves
Longitudinal or transverse
Longitudinal and transverse difference
Transverse waves cause the medium to move perpendicular to the direction of the wave (up down)
Longitudinal waves cause the medium to move parallel to the direction of the wave (bump shoulders)
Sound is longitudinal
Transduction
When a wave hits a surface, it causes the surface to vibrate the same way
Transduction is how acoustic energy is transferred from a source to a receptor while retaining the characteristics of the original
Mics and speakers are transducers
Concert A frequency?
Generally 440Hz, sometimes marginally higher
Does sound travel faster underwater or in air
Sound travels faster in water compared with air because water particles are packed in more densely. Thus, the energy the sound waves carry is transported faster.
Wavelength
The Wavelength of a waveform is the physical distance in a medium between the beginning and end of a cycle
Represented by lambda (Half Life symbol)
Equation for wavelength
λ=v/f
λ = wavelength
V = Velocity
F = frequency
Frequency
The rate at which an acoustic transmission completes cycles
Measured in Hz/Hertz
What is a cycle
One completed excursion of a wave, plotted over a 360degree axis of a circle is a cycle
(Circle shifted into place graph)
If it’s not a full cycle it’s an incomplete waveform
Amplitude
Analogous to loudness
Measured in decibels (dB)
Taller waveforms = more amplitude
Phase
Measured in degrees and is used to describe the relative phase degree angle with another wave(s) over 360º
Phase Shift
Phase shift describes one waveforms lead or lag time in relation to another. Essentially, a time delay
Waves that start at different times are out of phase
What are some possible phase scenarios
A. When two waves of the same frequency and amplitude are added, the amplitude is doubled.
(reinforced)
B. When two waves 180º out of phase are added, they are cancelled. The result is zero amplitude. (no sound!) This is referred to as completely out of phase.
C. When two waves partially out of phase are added, the result is partial cancellation and partial reinforcement.
Velocity and Frequency difference?
Velocity/Speed = how fast. Frequency = how often
Velocity
Velocity of sound is analogous to the speed of sound.
* Velocity changes depending on the medium and temperature.
* The velocity of a sound wave as it travels through air at 20ºC) is approximately 344 meters per second (m/sec) (or 1,130 feet per second (ft/sec))
What is wavelength measured in?
Metres
