Speech Science Exam 2

Incident wave

A sound wave that generated by a vibrating source, has traveled a certain distance and hit a boundary

Reflection

A portion of the wave that is not absorbed or transmitted, and is instead bounced back from the surface

Refraction

When a sound wave changes direction because of differences in air temperature (wave bends towards cooler air)

Diffraction

When a sound wave changes direction because of passing over an obstacle

Constructive interference

Sound waves combine to increase amplitude (2 zones of compression & 2 zones of rarefaction overlap)

Destructive interference

Sound waves combine to decrease amplitude (areas of compression and rarefaction overlap)

Be able to explain how the perception of sound is affected by reverberation and an echo

• Reverberation affects sound perception by making sounds last longer, increasing intensity, and making speech understanding difficult

• Echo affects sound perception by making a “second sound”, it is a type of reverberation

Be able to explain the difference between pitch and frequency

• Pitch = Perception of pitch (high vs low), subjective

• Frequency = Measured in Hz, objective measurement

Be able to explain what determines the frequency of a vibrating object

• Frequency of vibrating object depends on mass, tension, and length

• Increased length and tension, and decreased mass make a higher frequency

Be able to describe what is meant by the amplitude versus the intensity of a sound, and how these terms are related

• Amplitude = Maximum distance air molecules are displaced from rest during vibration, and maximum pressure change (measured in dynes/cm2 in cgs, or Pascals in MKS)

• Intensity of sound = The power of sound per unit area (measured in W/m2 in cgs, or W/cm2in MKS)

• Intensity = amplitude squared. This means that any increase in amplitude will lead to a way bigger increase in intensity

dB IL reference sound

10^-12 W/m^2 (MKS) or 10^-16 W/cm^2

dB SPL reference sound

20 Pa (MKS) or 0.0002 dyne/cm^2 or 0.0002 bar (cgs)

Know the difference between loudness and intensity

• Loudness is the perception of intensity, and is subjective

• Intensity is a subjective value, and can be perceived as “loud” or quiet”

• Larger intensity = “louder” perceived sound

Know the relationships between increases/decreases in intensity and how dB changes as a result

• Increased intensity = increased dB

• Decreased intensity = decreased dB

Know the relationships between increases/decreases in amplitude (pressure) and changes in dB as a result

• Increased amplitude = increased dB

• Decreased amplitude = decreased dB

Know what sounds are detected in our Auditory area and differences in thresholds of detection and pain based on hearing ability

• The threshold of hearing is 0dB

• The threshold of pain is 130dB, but with hearing loss can drop to 90dB

• Frequencies can be detected between 20-20,000 Hz

  • Standard speech is in 1,000-4,000 Hz range

Know what happens during free vibration and forced vibration

• Free vibration = Object is hit and vibrates

• Forced vibration = Vibrations from one object can start another object vibrating

Natural frequency

Each object’s own specific frequency at which it will vibrate freely

Be able to describe the relationship between applied frequency and a resonator

• Applied frequency = the original object in vibration

• Resonator = the object that is started into forced vibration by the applied frequency

Know the types of resonators discussed in class, especially acoustic resonators.

• Helmholtz Acoustic Resonator = vibrating container filled with air

• Half-wave resonator = tube open at both ends

• Quarter-wave resonator = tube closed at one end

Know what it means to say that resonators may filter a sound that is introduced to it

Sound waves that match the natural frequency of the resonator are amplified by vibrations, while sound waves that do not match the natural frequency are dampened (filtered out)

Be familiar with how sound waves vibrate inside tubes and how length affects that vibration.

• Longer tubes = a lower frequency

• Sound waves travel into and reflect off of the tube, creating a node at a closed end and an antinode at the open end

Node vs antinode

• Node = points along a wave that vibrate with minimum amplitude, happens at the closed end of tubes

• Antinode = points along a wave that vibrate with maximum amplitude/pressure change

Know the important difference between a half wavelength resonator and a quarter wavelength resonator

• Half-wave resonator = tube open at both ends, fits half a wave

• Quarter-wave resonator = tube closed at one end, fits a quarter wave

Be able to calculate the resonant frequencies of a quarter-wavelength resonator if you are given the length of the tube.

• Lowest resonant frequency has a wavelength 4x the length of the tube

• Highest resonant frequency is an odd multiple of the lowest resonant frequency

Be familiar with the concept of a standing wave

A wave pattern that appears stationary because two waves of the same frequency travel in opposite directions and interfere with each other, creating fixed points called nodes and areas of maximum movement called antinodes.

Bandwidth

The range of frequencies that a resonator responds to effectively; measured between the lower and upper cutoff frequencies.

Center frequency

The frequency at which a resonator has its strongest response; usually the middle of its bandwidth.

Narrowly tuned resonator

A resonator that strongly responds to a small/narrow range of frequencies; has a narrow bandwidth.

Broadly tuned resonator

A resonator that responds to a wide range of frequencies; has a broad bandwidth.

Cutoff frequency

A frequency marking the edge of a resonator's effective response; typically where the response drops to the half-power point.

Upper cutoff frequency

The highest frequency in the pass band before the response drops to the half-power level. 

Lower cutoff frequency

The lowest frequency in the pass band before the response drops to the half-power level.

Half-power point

The point where the output power is half of its maximum power, corresponding to about -3 dB

Pass band

The range of frequencies that a resonator/filter allows through or amplifies effectively.

Low pass filter/high pass filter/band pass filter/band stop filter:

Low-pass filter: Allows low frequencies to pass while reducing/attenuating higher frequencies.

High-pass filter: Allows high frequencies to pass while reducing/attenuating lower frequencies.

Band-pass filter: Allows a specific range of frequencies to pass while reducing frequencies above and below that range.

Band-stop filter: Blocks/reduces a specific range of frequencies while allowing frequencies above and below it to pass.

What are the major characteristics of the Vocal Tract Resonator?

The vocal tract is a variable resonator made up of the pharynx, oral cavity, and nasal cavity; changing its shape and size changes its resonant frequencies.

How do we determine the resonant frequencies of the vocal tract?

Resonant frequencies can be determined by analyzing the acoustic spectrum of the sound produced and identifying peaks in energy.

Formants

Resonant frequencies of the vocal tract, labeled F1, F2, F3, etc.; they are important for distinguishing different vowels.

What is the source filter theory of vowel production? (Understand the graphs that are associated with this theory that show the source, the filter, and the output we hear)

The source (vocal folds) produces a complex sound containing many frequencies, and the vocal tract acts as a filter that strengthens some frequencies and reduces others; the filtered sound is what we hear.

How do oral and pharyngeal volumes affect formants?

Changing the size/shape of the oral and pharyngeal cavities changes the vocal tract resonances and therefore changes formant frequencies.

What is important about our perception of vowels and formant frequencies?

We primarily identify vowels based on their formant patterns, especially the relationship between F1 and F2, rather than simply their fundamental frequency.

What are formant frequencies dependent upon?

The length and shape of the vocal tract, tongue position, jaw position, lip position, and the sizes/volumes of the oral and pharyngeal cavities.

Understand how tongue position (height and front to back placement), oral volume, and pharyngeal volume affect the values for F1 and F2 for vowels

Tongue height and F1: Higher tongue position → lower F1; lower tongue position → higher F1.

Tongue front/back position and F2: Front tongue position → higher F2; back tongue position → lower F2.

Oral volume and formants: Increasing or decreasing the volume of the oral cavity changes the resonant frequencies; a larger oral cavity generally lowers certain resonances, depending on the vowel configuration.

Pharyngeal volume and formants: Changes in pharyngeal cavity size affect the resonance pattern; larger pharyngeal volume generally lowers resonant frequencies

What do F1/F2 plots show you (what are they describing)?

Graphs that show vowels based on their first formant (F1) and second formant (F2) frequencies, showing how vowels differ acoustically based mainly on tongue height and front/back position.