تسجيل الدخول

تسجيل

SENSATIONS OF TONE

المؤلف:  Parviz Birjandi

المصدر:  AN INTRODUCTION TO PHONETICS

الجزء والصفحة:  C8-P175

2026-08-02

22

SENSATIONS OF TONE

The ears of an average young person are sensitive to all sounds from about 15 Hz to 20,000 Hz. The hearing of older persons is less acute, particularly to the higher frequencies. The degree to which a sensitive ear can distinguish between two pure notes of slightly different loudness or slightly different frequency varies in different ranges of loudness and frequency. Differences of about 20 percent in loudness (about one decibel, dB), and 0.33 percent in frequency (about 1/20 of a note) can be distinguished in sounds of moderate intensity at the frequencies to which the ear is most sensitive (about 1,000 to 2,000 Hz). In this same range, the difference between the softest sound that can be heard and the loudest sound that can be distinguished as sound (louder sounds are “felt,” or perceived, as painful stimuli) is about 120 dB (about one trillion times as loud).

 All of these sensitivity tests refer to pure tones, such as those produced by a tuning fork. Even for such pure tones the ear is imperfect. Notes of identical frequency but greatly differing intensity may seem to differ slightly in pitch. More important is the difference in apparent relative intensities with different frequencies. At high intensities the ear is approximately equally sensitive to most frequencies, but at low intensities the ear is much more sensitive to the middle high frequencies than to the lowest and highest. Thus, sound reproducing equipment that is functioning perfectly will seem to fail to reproduce the lowest and highest notes if the volume is decreased.