Table of Contents
A Word about Air and an Air about Words
Frequency is the number of times per second (cycles per second) that a molecule of air bounces (oscillates) back and forth.
We experience frequency as a range of Pitches from low (around 50 Hz) to high (around 20,000 Hz).
Our most sensitive hearing is in the range of frequencies that speech sounds are produced.
Consonants are high frequency sounds that are critical to understanding speech.
A Pure Tone occurs when a molecule oscillates regularly and smoothly back and forth.
Tones have Periodic (regular) oscillations, but Noise has Aperiodic (irregular) movements
Vowels are tones and originate in the larynx, whereas consonants are noises and are generated in the vocal tract.
An increase in the range of molecular oscillations (Intensity) will be perceived as an increase in loudness.
The Threshold of hearing is the intensity level of a sound which is perceived by the listener fifty percent of the time.
The range of hearing for loudness is so large that we must use a logarithmic scale to the base 10 to measure it.
Zero decibels (0dB) is the average threshold of hearing for the healthy adult ear.
Although it changes a little for each frequency, the air pressure at 0dB is about .0002dynes/cm2
A hearing threshold of 30dB or more for most frequencies in both ears would cause a significant speech and language problem
Phase is the interaction of two tones generated simultaneously
If two pure tones of the same frequency and intensity occur simultaneously out of phase, they will cancel each other out.
If two pure tones of different frequencies occur simultaneously they will cause fluctuations in the smooth curve to create a Complex tone.
The Fundamental in a Complex tone determines the pitch, and the pattern of Overtones determines the quality.
As the mass of a vibrating body increases, its frequency decreases, but as the tension increases the frequency also increases.
The pitch of one's voice is raised by increasing the muscle tension on the vocal folds in the larynx.
A person who is tense may have a habitually higher pitched voice that would be predicted from the mass of his vocal folds.
Our face and our voice are two important passports, that determine if and how we will be accepted into society.
Our Voice is a major component of our Self Concept
When the teenager's voice begins to change, a major part of his self concept is threatened.
In a desperate attempt to maintain the status quo for vocal pitch, some teenagers may adopt a falsetto register.
If mass and tension of a vibrating object are held constant, there will be one frequency at which it vibrates best.
A body will resonate if the original vibration matches the Natural frequency of the resonator.
A resonator is a screen that lets some frequencies of a complex tone through while inhibiting others.
The Expressive Transducer, and What Babies Hear
When breathing for life, inhalation is active involving many muscles and exhalation is passive.
When breathing for speech, exhalation is highly controlled, requiring special neurological circuitry which humans posses.
The Generator is a mechanism to produce sound , which is required for speech.
There are two passages leading from the oral cavity--one for food (Esophagus) and one for air (Trachea).
If liquid or food gets down the wrong tube (the Trachea) we may get pneumonia or worse yet, quick asphyxiation.
The Larynx (not to be pronounced "Larnyx") is a valve system at the top of the Trachea to keep food out.
In the Larynx, the vocal folds open and close to let air pass and to keep food from falling down the Trachea.
When the vocal folds are shut and air if forced through, they will vibrate and produce a sound.
The only changes in sound we can make at the level of the larynx is to raise and lower the pitch and loudness.
When the vocal folds are abused they may swell, which causes a drop in the pitch of the voice.
The greatest threat to the health of the vocal folds is smoking.
A person who has his/her larynx removed is called a laryngectomee.
A laryngectomee has no voice, and must use an artificial larynx or esophageal speech to communicate.
Esophageal speech takes time and effort to learn, and the artificial larynx sounds mechanical.
Juvenile Pappiloma is an aggressive growth on the larynx of some young children that requires medical attention.
A series of resonating air chambers above the larynx alter the overtones to create the human voice.
The Pharynx and the Nasal Cavity are two resonating cavities that shape the sound produced by the Larynx.
Only three sounds in English use Nasal Resonance: "m," "n," and "ng."
The Oral Cavity it the major Modulator of the three resonating cavities.
The Oral Cavity can produce phonemes with a minimal expenditure of movement and energy.
Actually, speech is not a series of discrete phonemes, but a continuous modulated flow of vocalized sound.
Babies do not perceive phonemes, but instead can hear all of the distinctive features that build the phonemes of every language.
Voice Onset Time is a good example of a distinctive feature that babies perceive, but we as adults may not.
It is advantageous to have speakers of other languages talk to babies who are not high risks for language delay.
The Place of Constriction of the air flow through the vocal tract is one distinctive feature for consonants.
The place of constriction can be described in terms of locations proceeding from front to back in the vocal tract.
The baby is capable of perceiving the constriction boundaries of English and all other languages.
In vocalizations, back consonants appear first during the reflexive stages, but front consonants appear first in the voluntary stages.
The Manner of Articulation is a second Distinctive Feature for Consonants.
The addition of a tone from the Larynx (+Voicing) to the noise of a consonant provides a third distinctive feature.
Nasality, a fourth distinctive feature of consonants, is used in only 3 phonemes in English: "M," "N," and "Ng."
The place of articulation for vowels refers to the arching action of the tongue to produce front, mid or back vowels.
In vocalizations, front vowels appear first during the reflexive stages, but back vowels appear first in the voluntary stages.
The tongue raises and lowers to produce an array of front and back vowels.
The position of the jaw will drop for low vowels to facilitate the movement of the tongue.
For some vowels, the tongue is more relaxed than for others.
Lip rounding is more essential for lip reading than for sound production.
Lip rounding is an important visual component in the perception of speech.
The key to good phonemic development is for the parents to spend much time talking to and around their baby.