Artificial Speech. The human voice is essentially an ever changing resonance tube. The lungs

Transcription

1 Artificial Speech The human voice is essentially an ever changing resonance tube. The lungs pump air through vocal folds creating sound that is then passed through articulators such as the tongue, palate, cheeks, and lips(1). Unfortunately, the vocal folds can be damaged by mistreating the voice. Nodules develop when the focal folds are stressed beyond their capacity. In the image below the vocal fold nodule is located near the bottom right(3). The development of nodules hinders the ability of the focal folds to regulate the changes in air pressure that make speech possible. There are also various forms of voice box cancer which may require the removal of one or both vocal cords along with radiation therapy(4). Fortunately for those who have lost the ability to produce their own voice, I have been playing with an idea to help them recreate speech at a cost much less than an artificial voice box.

2 Through careful research, more honestly by accident, I realized that when a concentrated stream of air was passed over the lips at the correct angle, sound was produced. As different words were shaped by the lips, tongue, palate, and cheeks, the air stream provided the necessary air pressure to make the words audible. First used as a cheesy physics pick up line, the idea soon developed into an eccentric voice box simulator. The simulator utilizes the mouth as a resonator. Unfortunately, the simulator lacks the ability to replicate the changing frequencies produced by natural voice resulting in a monotone imitation. The richness of tone comes from the body s multitude of resonance structures. The chest, neck, and diaphragm contribute to the changes in air pressure making frequency variation possible(1). Where the simulator contains few harmonics, the natural human voice contains a cast array as shown in the spectrogram below of a woman saying It s all Greek to me.

3 The simulator is only able to take advantage of the lips, tongue, teeth, oral cavity, hard palate, soft palate, and pharyngeal cavity in producing sound(2). Natural human speech resonates in most parts of the body, so naturally the simulator is unable to replicate that kind of power. The air stream is produced by a small canister of compressed air located at the user s hip. It is connected to a tube, which would be worn under the user s clothing. The tube is then mounted to an apparatus that secures around the user s ear and points at the mouth.

4 In the image above, the red line is the air tube, the green line is the microphone cord, and the gray is the apparatus that holds both of them in place. The sound produced by this set-up is very breathy, and doesn t reach the appropriate volume levels to be useful in an average lifestyle. To alleviate this problem a microphone is placed near the end of the tube to register the sound produced. The wire for the microphone is attached to the tube and also directed down to the hip underneath the user s clothing. The microphone, attached to a simple effects unit similar to a guitar pedal, would alter the tone and timbre of the sound. After being passed through the effects unit, the sound would be amplified and projected through a small speaker.

5 In the image above, the air canister is shown in light blue, the effects unit is orange, the battery is yellow and the speaker is pink. The canister can be used independently of the electronics. The canister of air, effects unit, and speaker would all fit in a small pack secured around the hip. The entire unit would run on a rechargeable battery that would need to be plugged into a power source every night. The simulator would be a less invasive alternative to traditional voice box replacement. Its cost effectiveness also makes it a consumer friendly option. People suffering from speech loss without health insurance would be able to purchase a

6 unit to assist them until they are able to afford more thorough medical attention. It could also be used simply as a toy for physics enthusiasts. Works Cited 1."Human Voice." Wikipedia. 3 May Wikimedia. 5 May 2008 < 2."Speech Production Physiology." Purdue University. 5 May 2008 < 3."Vocal Fold Nodule." Wikipedia. 2 May May 2008 < 4."Voice Box Cancer." The American Oral Cancer Website. 17 Feb American Thyroid Clinic. 5 May 2008 <