Sound Waves
Define Wave and list the shapes
A disturbance travelling through an elastic medium
It only carries energy NOT matter
1. Pulse
2. Sinusodial
3. Oscillatory
What type of tube is the vocal tract?
Open-closed
Define Beat Frequency:
is the difference between the two sound frequencies
The resonant frequencies of the air in the vocal tract are called
Formants
when a string get infinitely long then the discrete/dense spectrum results in:
A continuous spectrum
Transverse versus Longitudinal Wave
Transverse wave: the medium oscillates perpendicular to the wave velocity
- spring moves vertically up and down. Example: wave on a rope or guitar string
Longitudinal wave: the medium oscillates parallel to the propagation of the wave.
- spring oscillates back and forth. Example: sound waves
True or False: Closed-open ended air tubes do not posses even harmonics
True
Define Diffraction:
The bending of waves around small obstacles and the spreading out of waves beyond small opening
What is the source filter model?
describes speech production as a two stage process involving the generation of a sound source, with its own spectral shape and spectral fine structure, which is then shaped or filtered by the resonant properties of the vocal tract
True or false: The shaper the pulse the broader the spectrum
True
What are properties of a sound wave?
Loudness, pitch, pure tone, speed, medium of propagation
The sequence of possible frequencies is called a set of
Harmonics
Define: Doppler Effect
the change in frequency or pitch of the sound detected by an observer because the sound source and the observer have different velocities with respect to the medium of sound propagation
False - they are never heard because they are modified by the vocal cavities
Define Resonance:
The phenomenon of driving a system with a frequency equal to the system's natural frequency
How is a sound wave produced?
It is a pressure wave or a pressure disturbance; it needs a medium to propagate
It emanates from a source and vibrates at a frequency
If we change the frequency or the amplitude of a sinusoidal wave, What will change?
Sound quality
Timbre, tone quality, and tone color are used to describe sound quality
The reflection of sound waves off surfaces can lead to one of the two phenomena:
1. Echo: these occur when reflected sound wave reached the ear more than 0.1 second after original sound was heard
2. Reverberation: the persistence of sound after it has been stopped due to multiple reflections from surfaces such as furniture, people, air, etc., within a closed surface
Describe the Middle Ear Functions
Impedance matching: amplification of sound to overcome difference in impedance between air of EAC and fluid in the ear
Filtering: functions as bandpass filter
Acoustic reflex: contraction of stapedius muscle in response to loud sounds
In a string, the velocity of the wave is determined by:
The tension and linear density of the string (medium)
How is sound wave different from a light wave?
Sound is a mechanical wave and cannot travel through a vacuum. Light is an electromagnetic wave and can travel through the vacuum of outer space.
If wavelength increases and velocity is unchanged, then what happens to frequency?
If wavelength increases, what will happen to frequency?
It decreases
Frequency does the opposite of velocity
Sound is bent from original direction; Sound waves get refracted (bend in cold air) and therefore change their path downwards instead of disappearing into the upper layers of air. Thus, more sound is heard due to the additional bent waves.
What are the human hearing range of frequencies
20-20,000Hz
Subsonic versus supersonic
Subsonic means the speed being lower than the speed of sound, and supersonic means just the opposite.