I will undoubtedly get to use the terms « voice » and « speech » on a regular basis. Can these be considered as being equivalent, i.e. does voice = speech ?
The human voice results from impulses produced in the larynx: these are called the laryngeal impulses. The voice is ‘the sound emitted in the larynx » (1). The voice « possesses intensity, pitch and timbre characteristics, the timbre depending on the amount and relative proportion of the harmonic structures »(2).
The speech « is constituted of sounds that are generated when the airflow path is narrowly constricted, and that are modulated by articulation (1). This modulation of the voice « triggers timbre variations reminding of phonemes, and makes the voice the carrier of a message » (1). This « vocal timbre specifically defines speech »(1).
« The sound is mandatory to provide the speech with an acoustic structure, while the voice is the holder of speech information »(3).
« The voice embodies the acoustic support, the speech and a picture of cavity resonance, as a compulsory figure for the laryngeal sound »(4).
In the following citation, still from Professor J.C. LAFON, the reader will come across the cycle/second expression, which corresponds to the unit in place prior the Hertz: 1 cycle/second = 1 Hertz. « Men’s voices, the deepest among human voices, oscillate fundamentally between 80 and 250 cycles/second depending on subject and circumstances. The size of the larynx is an explanation to these rhythms. Naturally high-pitched women’s voices can vary, during speech, from 150 to 350 cycles/second on average… The even higher-pitched voice of a child results from the small size of the children larynx: it is highe than the average female voice, ranging from 250 to 500 cycles/second… Among other voices, the whispering voice is of particular interest: there is no laryngeal vibration anymore, but a laryngeal airflow instead. This phenomenon is then transmitted through resonators and enhanced, just as the normal voice. The frequencies being at an almost steady-state, cavities strengthening is thus clearly underlined. The resulting voice would be perfect for speech, should it not be so weak and in lack of deep sounds. Is thus has a low scope and the deep sounds generated are unusable for hearing »(5).
The deeper the laryngeal sound, the closer the harmonics, and so, the better the resonator’s representation – i.e. the better the phoneme’s representation. A man’s voice allows a good phonetic individualisation: it is more understandable than women’s or children’s voices, as these have loose harmonic structures »(6). The resonators I am referring to are the pharynx, the nose cavity, the mouth and the lips.
« The speech is relatively independent from the voice, it results from the shape of the resonant cavities… The voice corresponds to the acoustic support, while the speech represents the distortions inflicted to this support »(7).
« The melody is elaborated fromthe voice, and speech get structured upon that melody: there can be no verbal thinking if it cannot rely on speech »(8).
« The voice and the melodies are acquired over complex motor learning processes in the first few months »(9) of life.
« … there are only few differences between walk and speech, as there are based on organised moves, on movement. Speech, just as walk or children’s communication, is nothing else but a movement »(10).
« … speech is a movement translated into sounds through breathing »(8).
Alright, JYM, stop here ! We got it, voice and speech clearly are two different things!
(1) Prof. J.C. LAFON « word recognition test and hearing screening » page 51.
(2) Prof. J.C. LAFON « message and phonetics » page 91.
(3) Prof. J.C. LAFON « amplification with a counterbalanced order » Bulletin d’Audiophonologie 1971, N°2, Volume 1, page 181.
(4) Prof. J.C. LAFON « message and phonetics » page 89.
(5) Prof. J.C. LAFON « message and phonetics » page 96.
(6) Prof. J.C. LAFON « message and phonetics » page 98.
(7) Prof. J.C. LAFON Académie des Sciences (French National Academy of Sciences), séance du 20 mai 1959 page 2906.
(8) Prof. J.C. LAFON « hearing-impaired children » page 20.
(9) Prof. J.C. LAFON « hearing-impaired children » page 105.
(10) Prof. J.C. LAFON « talk on language writings, Délémont 1977 » page 13.
(translated from french by O.B.)