HOW WE TRANSMIT SOUNDS? Media and communication 김경은 김다솜 고우

CONTENTS INTRO GENERATING FREQUENCY MAKING HARMONICS VARYING INTESITY MAKING COMPLEX TONES CONCLUSION

INTRO

When we speak, we produce energy in the form of sound. Sound energy is a pressure wave consisting of vibrations of molecules The normal way of propagating sound is through the air.

INTRO The way air particles move ? To-and-fro movements Chain reaction Local unlike domino(backwards and forwards) forwards backwards

INTRO the way air particles move can be compared to a pendulum or a swing. A waveform graph Forward ; it compresses the adjacent particles and causes a tiny increase in the air pressure at that point Backward ; it decompresses these particles and causes a decrease in pressure.

INTRO pure tone simple waveforms consist of a single pulse of vibration that repeats itself at a constant rate. Pure tones are rarely heard in everyday life. To produce a pure tone, you need a special electronic machine, or a device such as a tuning fork. Pure tone

GENERATING FREQUENCY

a single to-and-fro movement of an air particle is called a cycle the number of cycles that occur in a second is known as the frequency of the sound. frequency used to be measured in cycles per second(cps), but this unit has been renamed hertz, named after the german physicist heinrich rudolf hertz

GENERATING FREQUENCY the range of frequencies that a young normal adult can hear is extremely wide(from about 20 to 20,000 hz) it is not possible to hear vibrations lower than this (infrasonic: 초저주파의 ) or higher than this (ultrasonic: 초음파 ). the most important speech frequencies lie between 100 and 4000 hz. the fundamental frequency of the adult male voice, for example, is around 120 hz, the female voice, around 220hz.

GENERATING FREQUENCY frequency correlates to a large extent with our sensation of pitch the notions of frequency and pitch are not identical. frequency is an objective, physical fact, whereas pitch is a subjective, psychological sensation. The difference between frequency and pitch

GENERATING FREQUENCY one way of relating the physical notion of frequency to our sense of pitch is to relate familiar musical notes to fundamental frequency. *middle C has a frequency of 264hz *middle A is the note sounded by the oboe when an orchestra is tuning up : that is 440hz. *the top note of a seven-octave piano is 3520hz, and the bottom note is 27.5hz.

MAKING HARMONICS

amounts of energy are also generated by the same vibration, all of which are correlated with the basic wave in a simple mathematical relationship: they are all multiples of the fundamental frequency(f 0 ). Thus an f 0 of 200hz will set up a ’sympathetic’ set of frequencies at 400 hz, 600 hz and so on. These multiples are known as overtunes, or harmonics, and numbered in sequence.

MAKING HARMONICS the difference we hear between two voices, or two musical instruments, when they produce a sound of the same pitch and loudness, is a contrast of timbre caused by the different harmonics.

VARYING INTENSITY

The greater the amplitude, the greater the intensity of the sound, the greater our sensation of loudness. Amplitude : the extent to which an air particle moves to and fro around its rest point. Thus, amplitude of the vibration indicates the intensity of the sound.

VARYING INTENSITY

To measure sound intensity? Departures from this reference level are then measured in units called decibels(db) Db? Sound intensities are related to each other as ratios, using a logarithmic scale. An increase of 10 db is roughly equivalent to a doubling of loudness. Example 30 db is twice as loud as 20db, 40 db is twice as loud as 30 db…

VARYING INTENSITY

It is also possible to work out average intensity values for individual speech sounds. [A:] ; vowels with the mouth wide open are the most intense sounds. [O:] and [i:] : vowels made higher up in the mouth. [R] and [l] : vowel-like sounds. [F] : much less intense are sounds involving a weak level of friction. [P] : those involving an articulatory closure and release. The decibel difference between adjacent sounds can be quite large. Thorn : the increase in intensity from the first sound to the second is nearly 30 db

MAKING COMPLEX TONES

Most sources of sound produce complex sets of vibrations, and this is always the case with speech. Speech involves the use of complex waveforms --- it results f rom the simultaneous use of many sources of vibration in the vocal tract. What is the complex tone ? Two or more pure tones of different frequencies combine ---- a complex tone

MAKING COMPLEX TONES Two kinds of complex tone (1) the waveform repeats itself -- A periodic pattern of vibration (2) no such repetition -- The vibrations are random, or aperiodic

MAKING COMPLEX TONES Make an acoustic analysis of the complex wave *Involved in a particular sound *Present its various components *It becomes possible to see various ’peaks’ of a coustic energy, reflecting the main points of res onance in the vocal tract. These peaks are known as formants.

MAKING COMPLEX TONES Formant ? Numbered from lowest to highest : the first formant (F1), the second forman t (F2), an so on. VOWEL FORMANTS

MAKING COMPLEX TONES Formant structure is a major feature of speech sounds that involve vo cal-fold vibration – all the vowels and all the voiced consonant. The formant pattern, especially the disposition of the first two formant s -- enables us to tell vowels apart or to recognize two vowels as bein g the ‘same’ Vowel formants can also help in identifying the character of adjacent consonant sounds. FORMANT

CONCLUSION

1.AIR / AIR PARTICLES 2.THE DIFFERENCE BETWEEN FREQUENCY AND PITCH 3.HARMONICS? 4.SOUND INTENSITY -> DB 5.PURE TONE AND COMPLEX TONE / FORMANTS

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