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Acoustic Analysis of Speech Signals, Exams of Health sciences

Oregon Health & Science University (OHSU)Health sciences

A comprehensive overview of acoustic analysis techniques used to study speech signals. It covers topics such as the characteristics of wide-bandwidth and narrow-bandwidth signals, the representation of nearly periodic sounds, the fourier transform, examples of vibration from different sound sources, the harmonic series, the limitations of acoustic analysis, and the parameters of speech spectrograms. The document also discusses the process of performing acoustic analysis, including improving the input signal, interpreting frequency domain displays, and the use of filters. Additionally, it covers concepts like clipping, motor equivalence, and the benefits of filtering speech. The document serves as a valuable resource for understanding the principles and applications of acoustic analysis in the study of speech production and communication.

Typology: Exams

2023/2024

Available from 08/27/2024

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ComD 5070 Exam 1 Acoustic Analysis
Solved 100% Correct
A 45 Hz bandwidth would be considered to be _______ __________. - ANSWER-
Narrow Bandwidth
A wide-band spectrogram is how many Hz? - ANSWER-300 Hz
All sounds originate with __________. - ANSWER-- MOVEMENT
- VIBRATION of air molecules
Characteristics of a wide-bandwidth. - ANSWER-- VERTICAL striations are GLOTTAL
PULSES
- ACCURATE TIME measures
Characteristics of narrow- bandwidth. - ANSWER-- HORIZONTAL bands are
HARMONICS
- TIME measures are NOT accurate
Describe a graphical representation of a nearly periodic sound. - ANSWER-- spectrum
does not have "pure" lines
- there are some peaks but there is some spread around the base of the peaks (which
represents the imperfection/NOISE that is present in EVERY human voice
FOURIER TRANSFORM - ANSWER-- take a time domain wave form (such as a mic
sig.)
- analyze it in such a way to create a spectrum which shows what the individual
components are
- analogy: take white light and put in through a prism and seeing the different colors that
come out
- going from one view of a signal to another view
Give 3 examples of vibration from different sound sources. - ANSWER-1) VIBRATING
string of an instrument
2) OSCILLATION of the vocal cords
3) TURBULENCE in air molecules leaving a tire
Harmonic Series: - ANSWER-- harmonics are MULTIPLES of the FUNDAMENTAL
- each line represents the harmonic frequencies
- has nothing between the lines (NO ENERGY BETWEEN the components)
If it is not harmonic in the voice, then it is ______. - ANSWER-NOISE
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Download Acoustic Analysis of Speech Signals and more Exams Health sciences in PDF only on Docsity!

ComD 5070 Exam 1 Acoustic Analysis

Solved 100% Correct

A 45 Hz bandwidth would be considered to be _______ __________. - ANSWER- Narrow Bandwidth A wide-band spectrogram is how many Hz? - ANSWER-300 Hz All sounds originate with __________. - ANSWER-- MOVEMENT

  • VIBRATION of air molecules Characteristics of a wide-bandwidth. - ANSWER-- VERTICAL striations are GLOTTAL PULSES
  • ACCURATE TIME measures Characteristics of narrow- bandwidth. - ANSWER-- HORIZONTAL bands are HARMONICS
  • TIME measures are NOT accurate Describe a graphical representation of a nearly periodic sound. - ANSWER-- spectrum does not have "pure" lines
  • there are some peaks but there is some spread around the base of the peaks (which represents the imperfection/NOISE that is present in EVERY human voice FOURIER TRANSFORM - ANSWER-- take a time domain wave form (such as a mic sig.)
  • analyze it in such a way to create a spectrum which shows what the individual components are
  • analogy: take white light and put in through a prism and seeing the different colors that come out
  • going from one view of a signal to another view Give 3 examples of vibration from different sound sources. - ANSWER-1) VIBRATING string of an instrument
  1. OSCILLATION of the vocal cords
  2. TURBULENCE in air molecules leaving a tire Harmonic Series: - ANSWER-- harmonics are MULTIPLES of the FUNDAMENTAL
  • each line represents the harmonic frequencies
  • has nothing between the lines (NO ENERGY BETWEEN the components) If it is not harmonic in the voice, then it is ______. - ANSWER-NOISE

If the ARTICULATION is disordered then we know something is wrong with the ______ ________ __________, necessitating a change in __________. - ANSWER-- MOVEMENT OF THE ARTICULATORS

  • FILTER If the VOICE is disordered then we know something is wrong with the ______ ________ __________, necessitating a change in __________. - ANSWER-- VOCAL FOLD MOVEMENT
  • SOURCE LINE SPECTRUM: - ANSWER-- SNAPSHOT in time SOURCE/FILTER THEORY OF SPEECH basic principle: - ANSWER-- SOURCE refers to the VOICE (sound coming out of the larynx from the vocal folds
  • FILTER refers to what the vocal fold does to SHAPE the SOUNDS that the larynx sends into it (ARTICULATION) SPECTROGRAM - ANSWER-- show speech OVER TIME (progression)
  • shows individual spectral slices that are arranged side by side overtime
  • they can show us how the frequency components can change overtime
  • very useful because speech is rapid succession with whole series of spectral characteristics Spectrograms are created from ______ ________. - ANSWER-Digital Recordings T/F. A Speech Spectrogram is both a Time Domain Display and a Frequency Domain Display. - ANSWER-TRUE.
  • it is a COMBINATION of both
  • it shows how the STRENGTH in each FREQUENCY in CHANGING over TIME T/F. A SPEECH WAVE is similar to a simple SINE WAVE. - ANSWER-FALSE.
  • speech waves are EXTREMELY COMPLEX because there are so many structures that contribute to the sound T/F. Acoustic Analysis can tell us everything about vocal tract movements. - ANSWER- FALSE
  • There are LIMITATIONS
  • it is useful but it doesn't perfectly reflect a linear 1:1 way the precise movements that went into making that sound T/F. If your sample rate is TOO LOW you can always "up-sample" later. - ANSWER- FALSE.
  • there is no way to "up-sample because you CAN'T REPLACE info that wasn't in the original recording. T/F. The human voice is nearly periodic. - ANSWER-TRUE.

What are you actually doing when you perform an acoustical analysis? - ANSWER-- splitting the sound apart and breaking it down to its "ingredients"

  • you then ALTER PROPORTIONS (same ingredients) which will ALTER QUALITY (just like baking)
  • you can have the some frequency components present in a sound but its the relative proportions that will determine the final quality What can you do to improve the input signal? - ANSWER-- some devices allow you to ADJUST THE RECORD INPUT LEVEL by twisting a knob or moving a lever until the sound is more clear
  • you can adjust the DISTANCE between the MIC and PERSON being recorded What do you get when you subject a time domain wave form to a Fourier Transform? - ANSWER-- a FREQUENCY DOMAIN DISPLAY
  • shows a spectrum that represents a snapshot in time that has FREQUENCY on its X- axis and AMPLITUDE on Y-axis
  • each COLUMN represents a FREQUENCY component What does a BAND PASS FILTER do? - ANSWER-- Allows a band of frequencies in the middle through but HOLDS BACK BOTH HIGHER AND LOWER FREQUENCIES What does a BAND REJECT FILTER do? - ANSWER-- HOLDS BACK A BAND (selected region) OF FREQUENCIES and allows both higher and lower frequencies through What does a band-width analysis show you? - ANSWER-- WIDE-band = GOOD TIME detail POOR FREQUENCY resolution
  • NARROW-band gives you GOOD FREQUECY detail but POOR TIME resolution What does a FILTER do? - ANSWER-- REMOVES IMPURITIES (particles that you don't want to have circulating) What does a FREQUENCY DOMAIN DISPLAY SPECTRUM show? - ANSWER-- INGREDIENTS in a sound in a SINGLE point in TIME
  • because it is NOT a time display, it does NOT SHOW progression of that signal over time What does a HIGH PASS FILTER do? - ANSWER-- Allows high frequencies through and HOLDS BACK LOW FREQUENCIES What does a LOW PASS FILTER do? - ANSWER-- Allows low frequencies through and HOLDS BACK HIGHER FREQUENCIES What does CLIPPING refer to? - ANSWER-- bringing in the signal at a level that is TOO HIGH
  • DRIVING the sound TOO HARD

What does NEARLY PERIODIC mean? - ANSWER-- REPEATS in a PATTERN ACROSS TIME What does NOISE look like? - ANSWER-- ALL FREQUENCIES are represented (vertical lines that are closely set against one another)

  • EQUAL AMP
  • RANDOM PHASE (APERIODICITY) What does REVERBERATION mean? - ANSWER-- ECHOING (from hard surfaces) What does SATURATION refer to? - ANSWER-- SIGNAL LEVEL as it comes into your recorder What does the line spectrum of a frequency domain data display show? - ANSWER-- the FREQUENCY COMPONENTS and PROPORTIONS of a periodic sound
  • the HEIGHT of each bar represents the STRENGTH of each component (ingredient in a recipe analogy) What happens if the strength of your signal is much bigger (clipping)than your recording device can accommodate? - ANSWER-- the signal will be BADLY DISTORTED
  • you WON'T be able to get a DECENT ANALYSIS -signal will have become CONTAMINATED with the noise that comes from "clipping" What happens if your SIGNAL LEVEL (saturation) is TOO TINY? - ANSWER-- it WON'T BE very AUDIBLE over the inherent background noise that is going to come from any recording. What is an FFT spectrum and what does it show us? - ANSWER-- FAST FOURIER TRANSFORM (FFT)
  • It is more revealing of the SOURCE (not filter)
  • shows us the RANGE of HARMONICS present in a complex sound (each peak is a harmonic)
  • does NOT show clear formants What is an LPC Spectrum and what does it show us? - ANSWER-- LINEAR PERSPECTIVE CODING (LPC)
  • shows a SPECTRAL ENVELOPE
  • GOOD at revealing FORMANTS (because of the way you have SHAPED the vowel, it doesn't matter if it from phonation or whispering
  • does NOT show individual harmonics (no details of sound source)
  • More revealing of the vocal tract FILTER or how the vocal tract SHAPES the sound given to it by the larynx (ARTICULATION)

When we apply the techniques that Fourier developed its called a _______ ________. - ANSWER-- applying a FOURIER TRANSFORM Who is Joseph Fourier? - ANSWER-- French Mathematician/Physicist 1768-

  • FOURIER THEOREM
  • came up with a way to analyze complex signals splitting them into individual sinusoidal components
  • all periodic sounds are made of a combination of sine waves with varying amplitudes, phases (where in the cycle they are relative to one another) and frequencies You need to sample at __x's the frequency of the _______ frequency component in order to accurately record and reproduce. This is called the _______ frequency - ANSWER-- TWO
  • HIGHEST
  • NYQUIST