Acoustics 1 Flashcards
Frequency
Pattern of pressure change or waveform that carries energy from the sound source as it travels away from the sound source through the medium of the air
Fundamental Frequency
Periodic sounds have a repeating pattern of compression, mechanical sound is oscillating at a regular rate. Oscillation frequency is known at the F0.
Periodic
Regular and repeating pattern of compression and rarefaction: Mechanical sound source and sound oscillating at a regular rate e.g.: voiced sounds/ vowels
Aperiodic Sounds
Produced by sounds that have no regular or oscillating movements, mechanical movement is irregular and chaotic: e.g. voiceless fricatives
Complex sound wave
More than one frequency: If not a pure tone it is complex sound wave
Simple Sound Wave
Periodic waveforms that only consist of one frequency: Sine waves and pure tones
Wavelength
Distance travelled by one cycle of the waveform: Related to frequency and velocity
Phase
Starting point of a cycle of a tone or frequency with respect to another tone
Amplitude
Amount of change in air pressure produced by a sound source- among of displacement of air particles from their point of equilibrium
Depicted by the vertical height on a time-amplitude waveform/ Amplitude (Hz)
Pascals:
Commonly used pressure scale: measures in terms of force per unit area
Decible
Ratio scale used to measure the amplitude of sound: How loud a sound is relative to the threshold of hearing
SPL: Sound pressure level (often used)
IL: Intensity level
intensity is directly proportional to square of the pressure
Spectral Analysis
Decomposes or analyses any complex function: such as sound wave into simple components
Spectrum/ visual display that shows the amplitude of the frequency components
Spectrum
Visual display that shows the amplitude of frequency components across a range of frequencies for a particular time
Harmonics
Frequencies that are multiples of the F0 are called harmonics
Pitch
Psychological correlate of F0 of a periodic sound wave
Loudness
Progresses slowly with physical dimension of sound intensity (volume)
Sone
Psychological scale of loudness
Mels
Psychological scale of pitch
Range of sound intensities humans can normal hear in dB
0 to 140 dB
Conversation
60dB
Loud Rock Music
120dB
Whisper
30dB
Range of sound frequencies humans can normally hear
20 to 20000
Comparison of physical scales of sound intensity and frequency with psychological dimensions of loudness and pitch
F0-pitch
Sound intensity/amplitude-loudness
Psychological dimensions are related non-linearly to physical dimensions, equal steps to changes in physical do not produce corresponding equal steps to psychological dimensions
What is the advantage of using the decibel scale rather than air pressure of intensity?
Decibel scale has small and manageable range of units compared to sound pressure level
What does zero dB mean
-
What is the Amplitude of Sound?
Amount of change in air pressure caused by a sound source
In periodic sound waves what is the period?
-
The F0 of human speech is associated with what part of the human speech production system?
Laryngeal system
Where are harmonics in speech created
-
What is the horizontal axis of a spectrum?
Frequency (Hertz)
What is the vertical axis of a spectrum?
Amplitude (dB)
What is the vertical axis of time-amplitude waveform?
Amplitude (Hz)
A simple sound wave is the same as a pure tone true or false?
true
what is the relationship between physical scales such as amplitude and psychological dimension such as loudness
As the physical dimension increases, more change is needed in the physical dimension to bring about a psychological change
What is a spectrogram?
Gives us information about the spectral energy of sound: shows how the spectrum changes over time
What is filtering?
Device that restricts or modulates the transmission of some part of the frequency spectrum. Can control the frequencies that are present in a sound by passing that sound through a filter
What is a low pass filter?
Transfers sound energy at frequencies below a certain cut off frequency eg passing sound below 5hz
High pass filter?
Passes energy above a particular cut off point eg passing everything above 500hz-variable in its way to increase or decrease cut off point
Bandwidth and band pass filter?
Range of frequency passed by a filter
Combination of both low and high filter and only transmits sound energy within a particular frequency range or band
Narrowband spectrograms components?
Useful for seeing the fundamental and harmonic frequencies- frequency resolution is good
Temporal resolution is poor so glottal pulsing is not visible
Longer window of analysis 30-50hz
Used if not much detail is needed
Bandwidth 30-50 hz
Harmonics are visible
Wide band filter components ?
Faster providing better time for resolution
Temporal window is 3-5 MS short time
Bandwidth 300-500 hz
Good temporal resolution therefore it is possible to see glottal pulsing or striations
Poor frequency resolution (Can’t see harmonics)
Information regarding vowel type can be seen
Does narrow band show you striations ?
False
Narrow band show f0
True
A sound passes through a filter which cuts all frequencies above 5000 hz what type of filter is it?
Low pass filter
What is the typical bandwidth for a narrowband spectrogram?
30-50hz
What is typical bandwidth for wide band spectrogram
300-500hz
Horizontal axis for spectrogram
Time
Vertical axis for a spectrogram
Frequency hz
What type of spectrogram has good frequency resolution but poor temporal resolution
Narrowband
Good temporal resolution but poor frequency resolution
Wideband
Horizontal axis of fundamental frequency contour and intensity contour?
Time MS
Vertical axis of a f0 contour?
Frequency hz
Vertical axis of RMS intensity contour?
Amplitude db
Resonance in speech is associated with?
The vocal tract or articulating system
For what vowel categories do formants 1 and 2 come close together
Back vowels
Central vowel vocal tract positions,compared to other vowels are most like what?
Closed end straight tubes
For what vowels do formants 1 and 2 remain far apart?
Front vowels
What is acoustic phonetics
Concerned with how different sound categories are realised in the speech sound wave
What is created by the source in the source filter theory of speech production?
Harmonics
What depends on the filter in the source filter theory of speech production?
Formant transitions
What do shorter vocal tracts have?
Higher formants frequencies
Diphthongs are characterised by?
Formant transitions with long durations, relatively slow transitions
Features of semi vowels
W j r l
Formant transitions esp 2nd Formant
Rate of change generally faster for semivowels than diphthongs
3rd Formant important in distinguishing between r and l- frequency of third Formant is lower for r
Japanese speakers have trouble distinguishing the two
Use of spectrums and spectrograms in clinic
Features of different sounds can be seen in these visual displays.
Eg misarticulating children saying tar instead of car should be reflected in spectrograms of their speech- 2nd Formant should start at a lower frequency when fronting velar compared to a correctly produced velar
Improved articulation also reflected in spectrograms and speech pathologist can see change before hear perceptually
For older children and adults sitting at a computer with PRAAT and providing examples of the correct production may be useful visual bio feedback to help them modify their output therefor praat can be used as a therapy tool
Which fricative is not affected by resonance in the cavity after the point of constriction
F
Which Formant transition is longer semivowels or diphthongs
Diphthongs
What are the characteristics features of only nasal/nasalised sounds
There is a Formant whose frequency is below the first Formant of most vowels
Antiformants
Which feature of the following is not a key acoustic feature of stop consonants
Anti formants
