Final answer:
The low dips in the spectrum where sound is absorbed at specific frequencies for nasal and fricative consonants are called anti-formants or zeros. These frequencies affect speech recognition and the characteristics of sound and can be influenced by environmental factors such as altitude.
Step-by-step explanation:
The points in the spectrum where sound is absorbed at specific frequencies, particularly for nasals, fricatives, and some other consonants are known as anti-formants in linguistic terms and as zeros in engineering parlance. These points signify places in the sound spectrum where acoustic energy is dampened. This phenomenon can occur at various places in the spectrum, from the low-frequency and long-wavelength end to the high-frequency and short-wavelength end. In linguistics, a new line of research suggests that environmental elements, such as altitude, may influence language sounds, evidenced by the prevalence of ejective sounds in cultures living at high altitudes.
Humans are particularly sensitive to sounds in the middle portion of the audible range because this is where most conversational sounds fall and is crucial for speech recognition and music appreciation. Hearing loss, on the other hand, typically shows a dip in the spectrum near the 4000 Hz frequency. Moreover, the fundamental frequency and its overtones, which are collectively referred to as harmonics, are critical in the production of sound in musical instruments and human speech.