Sound Theory Flashcards
Hertz is named after who? Why?
Named after Heinrich HertzHe was the first person to conclusively prove the existence of electromagnetic waves
What is the generally accepted range of human hearing?
20 Hz - 20 kHz
What affects the speed at which sound travels?
Temperature and density of the given medium
When a sound is louder, how does it affect the frequencies?
As sound gets louder the frequency response becomes more linear—you perceive all frequencies more evenly rather than perceiving some frequencies as being louder than others
What is the threshold of pain?
approx. 120 dB
How loud is normal conversation?
Approx 60 dB
What is white noise?
All frequencies at the same actual volume
What is pink noise?
All frequencies as the same perceived volume
DEF: diffusion
The scattering of sound waves evenly throughout a given space
DEF: refraction
A change in direction of a sound wave caused by the sound wave hitting a medium through which the sound travels differently
DEF: absorption
When sound waves are absorbed into a medium and converted from sound energy into heat
DEF: diffraction
The bending of waves around an obstacle or spreading out of waves beyond small openings
How do high frequencies react when diffracted?
They are highly directional either focusing as they pass through an opening or being blocked by an obstacle
What is the speed of sound at 21° C?
343.6 m/s (344 m/s rounded up)
How does density of a medium affect the speed of sound?
The more dense the medium, the faster sound travels. sound travels fastest in solids, then liquids, and more slowly in gasses
How does temperature affect the speed of sound?
Sound travels faster in warmer temperatures and slower in cooler temperatures
How do you calculate the distance a sound is travelling?
d = c x t (Distance = speed x time)
How do you calculate the time a sound will take to travel at a certain distance ?
t = d/c (Time = distance / speed)
How do you calculate the speed at which a sound is travelling?
c = d/t (Speed = distance / time)
What is sound, technically?
Sound is fluctuation in air pressure that uses a medium to propagate, reaches our eardrum, vibrates our eardrums and registers as sound in our brain
What are the two types of waves in which sound can travel?
Longitudinal and transverse waves
What two periods make up a single cycle of a sound wave?
A period of compression (increased pressure), followed by a period of rarefaction (decrease pressure)
What is a zero crossing?
The centre line of zero amplitude in a sine wave that is reflected in DAWS
DEF: reflection
Sound bouncing off a surface and returning in the direction from which it arrived
How does sound behave when reflected off a concave object?
Sound becomes more focused/stronger
How does sound behave when reflected off a convex surface?
It diffuses
DEF: Envelope
The way a sound’s amplitude changes over time
DEF: Attack
the beginning of the sound and the way it changes before it reaches its steady-state intensity
DEF: Decay
the rate at which a sound fades to silence
Formula for determining speed of sound at a given temperature?
c = 331 + 0.6 x t
DEF: Sustain
the steady state of a sound at its maximum intensity
What is the speed of sound at 0ºC?
331
DEF: amplitude
The amount of pressure being exerted on molecules in dB
what does RMS stand for?
Root Mean Squared
DEF: root mean squared (RMS)
a calculation of the average of values over a period of time to determine the average perceived loudness
What is the formula for calculating the length of a soundwave in meters?
λ = c / f
How do you determine the added frequencies that occur as a result of the combination and interaction of two sine waves?
calculate the sum of both and the difference of both
What is the formula for calculating phase shift in degrees?
Ø = Δt x 360 x f
measured in miliseconds
What is the formula for calculating phase shift in cycles?
Ø = Δt x f
What is the makeup of a triangle wave?
A sine wave plus odd harmonics, increasing in frequency and decreasing in amplitude stacked on top of each other
What is the makeup of a square wave?
a sine wave with odd harmonics, but has more harmonics than the triangle wave
What is the makeup of a sawtooth wave?
a sine wave with odd and even harmonics above the fundamental
Comparatively, how do pink and white noise sound to us?
White noise sounds very bright because of the way our ears perceive sound.
Pink noise sounds darker because there is more low end content
What does the fundamental tone determine?
pitch
How does a triangle wave sound?
sounds brighter than the sine wave because it contains higher frequencies as part of the sound rather than just the fundamental
How does a square wave sound?
brighter still than the triangle because it has more harmonics
How does a sawtooth wave sound?
brightest of all the basic wave shapes because it has the most harmonics; more nasal
Do sine waves start in or out of phase and by how much?
Sine waves start in phase
Do cosine waves start in or out of phase and by how much?
Cosine waves start 90º out of phase
DEF: masking
when a sound is covered up by another, louder/more harmonically rich sound in the same frequency range
Why do sound waves travel faster in warmer temperatures?
The air molecules have more energy at a higher temperature and vibrate faster enabling sound waves to travel more quickly
What is a longitudinal wave?
A wave in which the displacements of a medium are in the direction of or directly opposite to the direction of prolongation of the wave
What is a transverse wave?
A wave where the displacements of a medium are at a right angle to the direction of propagation of a wave
DEF: amplitude
With sound waves, amplitude is the extent to which air particles are displaced, which is experienced as the loudness of sound.
DEF: frequency
Frequency is the speed of the vibration, and this determines the pitch of the sound. Measured by the number of wave cycles that occur in one second, measured in Hz
DEF: phase
a single instant on a wave form
can also be an expression of relative displacement between two waveforms of the same frequency.
DEF: wavelength
the distance between successive compressions or rarefactions as shown in the diagram below
DEF: period
the time it takes to complete one cycle of the wave form. As the frequency decreases, the period of the wave form increases
explain critical bands
the human ear can distinguish changes in frequency more easily at low frequencies than high frequencies. There are 24 critical bands in the human hearing range.
if two tones are in the same critical band they are not distinguishable as separate tones and instead the ear perceives the separate tones as modulating, beating, or masking.
What is masking
when the perception of one sound is affected by the presence of another sound, effectively covering up the sound and making it harder to hear.
how many critical bands exist in the human hearing range?
24
What is the cocktail party effect?
The brains ability to focus on one particular sound or stimulus while filtering out a range of other stimuli, like how a party goes can focus on a single conversation in a noisy room
