Теоретическая фонетика английского языка
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Зырянова Теоретическая фонетика
2.1. A
COUSTIC A SPECT OF S PEECH S OUNDS As V.A. Vassilyev points out, sound is a physical phenomenon, a kind of energy generated by some vibrating body (a string, a tuning fork or the vocal cords) set into vibration by the application of some external force (a blow or the pressure of air). This energy travels in waves through the air and another medium. Sounds can be periodical (the vibrations of a physical body are rhythmical) and non-periodical (the vibrations are not rhythmical). The auditory impression of periodical waves is a musical tone. The auditory impression of non-periodical waves is noise. 20 The sound has a number of physical properties which all exist and manifest themselves simultaneously, but each of them can be singled out and separated from the others for purposes of analysis. V.A. Vassilyev remarks that the first property is frequency which is the number of vibrations per second. Sound waves may follow one another at different rates of frequency. Therefore, the number of vibrations per second varies greatly. Dependent on the frequency of vibrations is the length of the sound wave, i.e. the distance between the points having the same phase (position) in two adjacent waves. Wave length is proportional to the frequency of vibrations: the higher the frequency, the shorter the wave length. Our perception of the frequency of repeated pressures on the ear- drum is the pitch of the sound. The greater the frequency, the higher the pitch, and vice versa. The frequency of the sound depends on the mass, length and tension of the vibrator. The greater the mass of the vibrator, the slower its vibrations, and the lower the pitch. Some people’s vocal cords are thicker and heavier than those of others and their voices are lower than the voices of those with thinner and lighter vocal cords. The longer the vibrator, the slower the vibrations, the lower the frequency and the pitch. A man’s voice is lower than a woman’s partly because his vocal cords are longer. As the tension increases, the frequency increases and the pitch rises. The second physical property of the sound is intensity, changes in which are perceived as variations in the loudness of the sound. The intensity is produced by the amplitude of vibrations and it is measured in 21 decibels. The intensity and frequency of the sound are closely interdependent. Sounds can only exist and move in time. In other words, any sound has a certain duration. The duration, or length, of a sound is the quantity of time, during which the same vibratory motion is maintained. For this reason, the duration of a sound is often referred to as its quantity. The duration of speech sounds is usually measured in milliseconds. In speech there are no definite boundaries between different speech sounds: one speech sound gradually passes into another. Therefore, it is extremely difficult to measure the length of speech sounds exactly. These physical properties of speech sounds will be referred to further in this course. Download 1.19 Mb. Do'stlaringiz bilan baham: |
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