Voice
The human voice is of vital importance to our everyday lives; the ability to produce sound is imperative for daily communication and many different forms of expression. Because we use the voice so much, its use and complexity can be taken for granted. With this in mind, the reader should be able to develop a greater understanding for the mechanics of the voice and sound production.
Figure 1.1 The human vocal folds are roughly 10-15 mm in length, and 3-5 mm thick
The human voice originates in the vocal cords, which are located in the larynx, or the voice box (a part of the throat). The vocal cords are made of mucous membrane, a membrane that lines many tracts and structures of the body such as the mouth, nose, eyelids, windpipe and lungs, stomach, and intestines. They are roughly 10-15 mm in length, and 3-5 mm thick (see figure 1). The larynx is a tube about 10 to 12 centimeters long and two centimeters wide, and its walls are covered by 16 to 20 horseshoe-shaped cartilage rings (1). The larynx is located at the top of the trachea, or the windpipe, which we use when we breathe, talk, or swallow. Each time we inhale air goes into our nose or mouth, then through the larynx, down the trachea, and into our lungs. When we exhale, the same happens in the opposite direction. In breathing, the vocal cords relax and air moves through the space between them (3).
As we speak, muscles in our larynx tighten the vocal cords, making this small space become narrower. The pitch of our voice is controlled by making this space narrower for a higher pitch and less narrow for a lower pitch (2). In addition, we can control the amplitude, or loudness, with the cords. When air from our lungs passes through the tightened cords a vibration is produced. The tighter the vocal cords, the more rapidly the vocal cords vibrate, producing a higher pitch and frequency (4). The sound that vocal cords produce is sent through the throat, nose, and mouth, giving the sound "resonance," a term describing a state in which an increased amplitude results in a clearer, more stable sound (see figure 2). It is important to note that the sound of each
individual voice is determined by the size and shape of the vocal cords in addition to the size and shape of the throat, nose, and mouth (the resonating cavities) (5).
individual voice is determined by the size and shape of the vocal cords in addition to the size and shape of the throat, nose, and mouth (the resonating cavities) (5).
Figure 2.1 The lungs, throat, mouth, and nasal cavities, where sound resonates.
The vocal tract, informally thought of as a megaphone, is the airway used in the production of speech, especially the passage above the larynx, the mouth, and the nasal cavities (7). To achieve a specific or consistent sound, sound must be produced by forcing air through a small opening in the glottis (the top of your throat), which is formed by the vocal cords. The glottis allows the vocal cords and the column of air above them to vibrate. As demonstrated by trained singers, this function can be closely controlled and finely tuned.
Some studies suggest that hormones play an important role in vocal fold development and maturation. The effect of hormonal changes in voice is demonstrated when hearing male and female voices (different sounds and qualities of the voices after maturation), or when listening to a teenage voice changing during puberty. What happens during this change is the larynx grows bigger. The larynx is responsible for creating the sound of the voice. It is believed that the number of hormonal receptors in the pre-pubertal phase is higher than in any other age. Menstruation has also been seen to influence the voice. Singers are encouraged by their instructors not to perform during their pre-menstrual period, because of a drop in their voice quality (6).
Figure 3.1 Vocal nodules where the vocal cords can no longer come together.
There are many disorders to the vocal cords that are often caused by vocal abuse or misuse, such as excessive use of the voice when singing, talking, smoking, coughing, yelling, or inhaling irritants. Some of the more common vocal cord disorders include laryngitis, vocal nodules, vocal polyps, and vocal cord paralysis. Vocal nodules, the most common of the vocal disorders, are non-cancerous growths on the vocal cords caused by vocal abuse. The nodules are small and callous-like and usually grow in pairs (one on each cord) and form on areas of the vocal cords that receive the most pressure when the cords come together and vibrate (similar to the formation of a callous). Vocal nodules are a frequent problem for professional singers (5). When a person has vocal nodules their vocal cords can no longer completely adduct, or, come together (see figure 3). The voice can have a raspy quality, and a person with nodules may experience the feeling of needing to clear the throat frequently, as the body senses a foreign object on the vocal cords. When looking at a raspy voice on the FFT, the shape of the sound waves appear broken, due to the inconsistency of vibration when the chords come together. Voice therapy involves teaching good vocal hygiene, reducing/stopping vocal abusive behaviors, and direct voice treatment to alter pitch, loudness, or breath support for good voicing (ASHA).
With that in mind, the goal for my project was to collect data that supports the improvement on pitch accuracy and harmonics produced by both singers and non-singers. For singers, accuracy would be dependent upon the comparison between the sound with or without vibrato. For non-singers, accuracy would be compared to their natural attempt at singing a pitch, and to the sound they produce after improving their posture and breath. In both of these groups, the expected results were to see a difference in their best attempt, and an increase in their overtone frequency level.
The experiment proved that my hypothesis was incorrect, after discovering that the results were much the same from both attempts to sing the given frequency. This was the case for both the non-singers and singers. This was also true for the presence of overtones. There is only one participant that challenged this statement; non-singer #4. The frequency they were asked to produce was a 327 Hz (E). Their sound wave results were of poor quality in all attempts, and because of this their overtones were either unidentifiable or not present. Non-singers 1 and 3 both showed a decrease in frequency of their overtones from their normal to improved attempts. This was contrary to the initial belief, because it had been anticipated that by improving posture and breath would create an increase in the overtone frequency. Non-singer #2 did demonstrate my prediction, however.
The results for the singers using vibrato and straight tone were very interesting. There were two of three singers who had a naturally large vibrato. In vibrato, the voice is alternating subtly and very quickly between two pitches that are very close together. Vibrato is different from straight tone; singing with straight tone forces the voice to produce a smooth sound without a variation in pitch. Singer #3 has a voice that sounds closer to straight tone than the other two voices; this can be why singer number three had the same results, with the exception for her first overtones for both attempts. Singer 1 and 2 contrasted in their results; singer one had an increase in accuracy and increase in overtone frequency when singing without vibrato (straight tone). Singer 1 also was able to produce an overtone when singing straight tone. This was the opposite for singer 2, who had a decrease in the accuracy of the pitch when singing with straight tone. In addition, singer 2 did not produce any overtones in any try.
In order for the experiment to be more accurate, there would need to be more variety in the participants. For example, gender and age would need to be considered in both singers and non-singers. Because the people used in the experiment were all women and there were not a large or equal amount of participants in each group, the lab did not produce enough information to fully make a conclusion.
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