Presentation on theme: "Fundamental Frequency & Jitter Lab 2. Fundamental Frequency Pitch is the perceptual correlate of F 0 Perception is not equivalent to measurement: –Pitch="— Presentation transcript:
Fundamental Frequency Pitch is the perceptual correlate of F 0 Perception is not equivalent to measurement: –Pitch= intensity, spectral characteristics –F 0 is determined by rate of vocal fold vibration Fundamental frequency is often used in voice assessment
Fundamental Frequency F 0 = cycles per second Hz= 1 cycle per second t (period)= duration of a single cycle t=1/ F 0 F 0 =1/t
Fundamental Frequency Instrumentation- –Visipitch II, CSL, MDVP, Oscilloscope –All instruments are not equal –Some instruments allow you to choose the sample section you wish to analyze Example of collecting F 0 from each instrument
Maximum Phonational Frequency Range (MPFR) MPFR= Lowest sustainable model-register tone to the highest falsetto-register tone All frequencies not used in connected speech MPFR may indicate a vocal pathology –reflection of reduced vocal flexibility and adjustability Example- Two oscillograms (High and low)
Normative Data: F 0 MPFR- Baken Text (Pg. 185-190) –*look at other sources listed under table- p.188 Speaking fundamental frequency- Baken Text (Pg. 186) –*Difference between speaking F 0 (SF 0 ) using connected speech, and F 0 obtained using a sustained vowel. –*Look in your voice text (Colton & Casper) for sustained vowel F 0.
Visipitch There are many versions of this instrument CSL has a Visipitch component The older Visipitch has a less reliable frequency counting system
Dysphonic Speakers CSL- Voice Disordered database Can take disordered voice samples from CD-Rom Analyze them as you would your own sample Use manual for description of patient
Fundamental Frequency Contours Connected speech consists of varied fundamental frequency Disordered speech/ voice physiology may impair the client’s ability to produce a normal intonation contour Contour should gradually descend
Fundamental Frequency Contour: Identify: *Lowest F 0 *Highest F 0 *Describe contour?
Speaking Fundamental Frequency Best measure of the client’s phonatory system use (mean speaking F 0 (SF 0 )) –Mean SF 0 = the average of frequencies used in an utterance Perceived as an abnormal habitual pitch –Pitch = standard deviation Measure of how much F 0 varies in an utterance Abnormally high or low pitch indicates speaker does not adjust phonation correctly when speaking Perceived as “monopitch” or “tremulous”
CV Utterance- /si/ “see” Mean SF 0 Pitch Describe contour?
CV Utterance Could this utterance be used to describe this speaker’s vocal frequency use? Why? Why not? –Length –Pitch –Loudness What might you use to describe vocal frequency use?
Frequency Trace: “Rainbow Passage” Extract 3rd sentence Highest F 0 Lowest F 0 Mean S F 0 Pitch
Vocal Jitter: F 0 Perturbation Frequency of a speakers voice will vary from one cycle to the next The random period variability= frequency perturbation or vocal jitter Vocal jitter increases in voice disorder & is responsible for hoarse, harsh or rough voice quality Jitter is a measurement of vocal stability Normal voices are usually less than 1% frequency variability
Types of Jitter Measurement Mean Absolute Jitter: –mean absolute difference between sequential vocal periods measured during a sustained phonation (measured in seconds or milliseconds) Mean Percent Jitter & Jitter Ratio: –taking the mean absolute jitter & dividing it by the mean vocal period used during the phonation, the proportion is then multiplied by 100 to get a %age; if the proportion is multiplied by 1000 it is called jitter ratio and is dimensionless
Types of Jitter Measurement Relative Average Perturbation (RAP): –Relative jitter measure that attempts to reduce the effects of long term F 0 changes, such as slowly rising or falling pitch. –Compares average of three cycles to given period. Averages 3 periods or cycles and compares it to the given period. The average difference is then divided by the mean period. If multiplied by 100 then it is called RAP%
Types of Jitter Measurement Mean Jitter Factor: –mean absolute difference between sequential vocal frequencies divided by the mean frequency of phonation, this proportion is then multiplied by 100 Frequency equivalent of mean percent jitter
Calculating Jitter Period (t) in ms Jitter in ms Mean period Mean F0 Mean absolute jitter Mean % jitter= Mean absolute. Jitter/mean period x 100 Time (ms)
Calculating Jitter Mean jitter factor= difference between sequential frequencies/ mean frequency
Vocal Shimmer: Amplitude Perturbation Same as frequency perturbation, but analogous to amplitude Amplitude perturbation or vocal shimmer serves as an index of vocal stability Excessive shimmer= perception of hoarseness A mean cycle-to-cycle amplitude difference of 0.7 dB or less variation or less than 7% of mean amplitude is normal
Types of Shimmer Mean Shimmer in Decibels: –mean absolute dB (SPL) difference between sequential vocal amplitudes measured during a sustained phonation Mean Shimmer in Percent: –mean absolute cycle-to-cycle difference in vocal amplitude divided by the mean amplitude then multiplied by 100 to yield a % age
Types of Shimmer Amplitude Perturbation Quotient: –Analogous to RAP, the amplitude perturbation quotient (APQ) attempts to desensitize long- term amplitude changes; APQ uses 11 point averaging (average of 11 cycles). The average amplitude differences I divided by the mean period