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From traffic noise to music, from birds and animals to the whistling wind, the sound is present everywhere. Humans and other organisms have the ability to produce sound through the larynx and capture sound by using the ears. Yet, there is another aspect of sound, which is Speech, something that only humans possess.
- Humans can produce sounds of different tones, pitch, and Amplitudes.
- Humans are not only gifted with the ability to produce sound but also Speech, which makes humans stand out from other species.
- There is a biologically technical mechanism behind the process of sound production by humans.
- This mechanism has three essential components- Lungs, articulators, and larynx.
| Table of Content |
Key Terms: Human Voice, Sound, Sound Waves, Larynx, Pharynx, Vocal Cords
Sound and Sound waves
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Every day sounds from various sources are heard. For example, the sound of a Church bell, a school bell, the horn of a car barking of dog music from different instruments, etc. Although sound can not be seen coming to us, sound reaches human ears in the form of waves formed due to vibrations of the particles of the medium.
In general, sound is that energy that stimulates the ears and helps humans in being aware of their surroundings.
- Sound produces a hearing sensation in the human ear.
- A vibrating object serves as a source of sound.
- A material medium like air is necessary for the propagation of sound from one place to another.
- Sound cannot travel in a vacuum.
Activity
Here is an activity to understand the concept better:
- Take a rubber band.
- Now, Stretch the rubber band by holding one side of the mouth between the teeth and the other side with one hand.
- Now, pluck it in the middle by using the other hand.
Observations reveal that the string initiates vibrations, accompanied by the generation of a sound. After some time when the strings stop vibrating, no sound is heard.
- The initiation of vibrations in a body to produce sound necessitates the presence of mechanical energy.
- The vibration of the body is transmitted in the medium in the form of waves from that point to the next and so on.
- When these waves reach the ears, they produce vibrations in the ear drum which are perceived as sound by Humans.
The vibrations of a vibrating body produce a periodic disturbance in the medium near it. This disturbance is then propagated in the medium in the form of sound waves.
Characteristics of Sound Waves
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Here's a list of several Characteristics of sound waves discussed in brief:-
- Amplitude: The amplitude of a wave is the maximum displacement of the wave from its mean position on either side as it passes through a medium. Its SI unit is metres.
- Time period: The time taken by the wave to complete its one cycle is called the time period of the wave. Its SI unit is second.
- Frequency: The frequency of a wave corresponds to the number of vibrations it completes in one second. It is also the same as the number of waves passing through a point in one second. Its SI unit is hertz.
- Wavelength: The wavelength of a wave is defined as the distance it covers during one time period. Its S.I. unit is a meter. Its value depends on the medium in which the wave travels.
- Wave velocity: The wave velocity or wave speed refers to the distance covered by a wave in one second. Wave velocity, also known as wave speed, refers to the rate at which energy is transferred from one location to another through wave motion. Its SI unit is a meter per second (ms_1).
Also Read: Beats
The Human Voice
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Talking, laughing, screaming, shouting, murmuring, crying and many other such actions are actually the different types of sounds produced by humans. The cords are the main components in the generation of human Voice and so speech. The vocal cords regulate the frequency of the voice of an individual.
- Other sound-producing mechanisms include unvoiced consonants, clicks, whispering, and whistling, all these are also generated from the same area of the body.
- Among the variations of sounds produced by an individual, the sounds produced by women, children, and men are very different and distinguishable from each other in general.
- The reason is that women, children, and men all have different sizes and lengths of vocal cords.
- Vocal cords (also called vocal folds) are responsible for producing and channelling vibrations that produce sound waves.
Vocal Cord
The voice of men is generally lower pitched as they have greater vestibular fold throughout adulthood and their vocal cords are about 20 mm long. For women, their vocal cords are shorter (15 mm long) and have a lesser number of vestibular folds. Children still have shorter vocal cords that make their voices different from men and women.
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How do humans produce Sound: Process
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Sound is produced by a vibrating body, while sound is propagated by the material medium around the sound source. The vibrating body creates a disturbance in the medium by striking its molecules. Now this disturbance is carried on further as one molecule hits the other molecules and so on. This is basically how sound is propagated.
- For in the case of humans, the larynx is responsible for producing sound waves. The other essential components are the lungs and the articulators (pharynx, tongue, saliva, palate, cheeks, lips, and other parts of the vocal tract).
- The human larynx is positioned at the apex of the windpipe and its topmost part is guarded by the cartilages- epiglottis and the corniculate cartilage. The opening between these cartilages has a pair of ligaments called the vocal cords ( also known as vocal folds).
- The vocal cords are attached to sets of muscles known as the vestibular folds. The contraction and relaxation of these muscles regulate the movement of the vocal cord hence, control the opening and closing of the laryngeal tract.
- When a person is not speaking, the laryngeal opening has the vocal cords wide apart. As soon as the person starts speaking the vestibular fold muscles tighten and the vocal cord sticks close to each other and as a result, the opening gets closed.
- Now, the vocal cords move slightly apart, opening as a narrow slit. The air from the lungs has a passage to move out.
- The air gushing out of this slit causes vibrations in the vocal cords. These vibrations create audible pulses making up a laryngeal sound source.
- Now, there is a need to tune the pitch and tone of the sound. This is brought about by changing the length and tension of the vocal cords.
- The role of articulators is to filter the coming sound waves to produce speech and make the sound more clear.
Also Read: Difference Between Larynx and Pharynx
Organs involved to produce sound in Humans
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The system that produces human voice can be roughly divided into three main components:
- Lungs
The lungs are a pair of organs that help in breathing and respiration. By sending out air through the laryngeal opening and causing vibrations in the vocal cords, it plays a key role in Voice Generation.
- Articulators
The parts of the mouth and throat that come in direct contact with the produced sound waves and modify these waves to an extent are known as Articulators. These usually include the following:
- Tongue and Palate - It helps in speech and pronunciation.
- Upper and lower lips- These, along with helping in pronunciation, modify the quality of the sound so produced and filter it.
- Gums and Teeth- It also plays an important role in speech by making the sound and tone clear.
- Glottis- When air is struck on the glottis, it lowers the pressure in the larynx. Consequently, the vocal cords begin to vibrate.
- Larynx
Location and Structure:-
- The human larynx is positioned at the apex of the windpipe and its topmost part is guarded by the cartilages- epiglottis and the corniculate cartilage.
- The opening between these cartilages has a pair of ligaments called the vocal cords ( also known as vocal folds).
- The vocal cords are attached to sets of muscles known as the vestibular folds.
- The contraction and relaxation of these muscles regulate the movement of the vocal cord hence, control the opening and closing of the laryngeal tract.
Larynx Functions:-
Below are the functions of the larynx:
- Vocal cords contained in the larynx function to produce sound.
- The vocal cords also modify the tone and pitch of the sound by changing its length and tension.
- It also helps in regulating the airflow in and out of the lungs while speaking.
Also Read:
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Things to Remember
- A sound is a form of energy that is produced by a vibrating body, this on reaching the ears gives the sensation of hearing.
- Sound needs a material medium to propagate. It propagates as sound waves. In a vacuum, sound can never travel.
- Sound waves are mechanical in nature and possess the following Characteristics- amplitude, frequency, time period, wavelength, and wave velocity.
- In humans sound is produced by these three parts- the lungs, the larynx, and the articulators.
- The larynx is known as the voice box. It is situated at the top of the windpipe and has vocal cords at the topmost opening.
- The vocal cords are responsible for producing sound and it also changes the frequency and quality of sound so produced.
- The voice of men is generally lower pitched as they have greater vestibular fold throughout adulthood and their vocal cords are about 20 mm long.
- For women, their vocal cords are shorter (15 mm long) and have a lesser number of vestibular folds.
Sample Questions
Ques. How many different sounds do humans make? (1 Mark)
Ans. Humans have the impressive ability to produce over 2000 distinct sounds, spanning from common sounds like 'm' and 'a' to the uncommon clicks found in certain South African languages.
Ques. How is sound propagated in air, explain. (5 Marks)
Ans. The propagation of sound in air can be explained with the help of the given example-
Take a thin metal strip. Keep it vertical, and fix its lower end. Press the upper end to one side and then let it go. As it vibrates sound is heard.
As the strip moves from left to right, it pushes the particles of air in front and at the back of it. So, the particles of air get closer to each other. This forms a compression in that region. As the strip retreats back to its mean position, the particles of air near it start returning back to their mean positions.
Now when the strip moves from right to left. It produces a region of low pressure on its right side. This region has rarefied air layers and is known as the region of rarefaction.
A single complete back-and-forth movement of the strip creates both compression and rarefaction, which together form one sound wave.
The wave in which particles of the medium vibrate back and forth along the direction of sound propagation is referred to as a longitudinal wave. The sound travels in the form of sound waves.
As the strip moves repeatedly to the right and left, it creates compression and rarefaction regions one after another, carrying the disturbance with a definite speed depending on the nature of the medium.
Thus, the sound is propagated in the air.
Ques. What do you mean by the audible range of frequency? (1 Mark)
Ans. The audible range of frequency refers to the range of frequencies within which a human being can hear sound. The audible range of frequency for humans is 20 hertz to 20 kilohertz.
Ques. How is the frequency of a wave related to its time period? (1 Mark)
Ans. The frequency of a wave is the reciprocal of its time period
Frequency= f = 1/T. (T – Time Period)
Ques. What are the functions of the larynx in the production of human speech? (2 Marks)
Ans. The functions of the larynx are as follows:-
- Vocal cords contained in the larynx function to produce sound.
- The vocal cords also modify the tone and pitch of the sound by changing its length and tension.
- It also helps in regulating the airflow in and out of the lungs while speaking.
Ques. What do you mean by articulators, when it comes to voice production in humans? State the functions of the different articulators. (3 Marks)
Ans. In human speech production, The parts of the mouth and throat that come in direct contact with the produced sound waves and modify these waves to an extent are known as Articulators. These usually include the following:
- Tongue and Palate - It helps in speech and pronunciation.
- Upper and lower lips- These, along with helping in pronunciation, modify the quality of the sound so produced and filters it.
- Gums and Teeth- It also plays an important role in speech by making the sound and tone clear.
- Glottis- When air is struck on the glottis, it lowers the pressure in the larynx. Consequently, the vocal cords begin to vibrate.
Ques. Explain why in thunder, light is seen much earlier than the sound of the thunder is heard. (2 Marks)
Ans. In thunder, light is seen much earlier than the sound of thunder is heard all those are produced simultaneously. The reason is that light takes almost negligible time in comparison to sound in reaching human ears from the place of thunder because the speed of light is much more (3 × 10-8 m/s) than the speed of sound (~330 m/s).
Ques. State two factors that affect the speed of sound in the gas. (2 Marks)
Ans. The speed of sound in a gas is affected by the following parameters:-
- Density: The square root of the gas density plays a vital role in sound speed variation. Due to the significant density difference (16 times) between hydrogen and oxygen, hydrogen's speed of sound is four times that of oxygen.
- Temperature: The speed of sound in a gas boosts with the increase in temperature of the gas. The reason is that as humans rise in temperature the density of gas drops and accordingly the speed of sound boosts.
Ques. What are the three characteristics of the medium needed for sound propagation? (3 Marks)
Ans. Requisites of the medium for the propagation of sound. The medium required for the propagation of sound must possess the following three properties:
- For sound propagation, the medium should possess elasticity, allowing its particles to return to their original positions after displacement on both sides. In other words, the particles are capable of vibrating around their mean positions.
- For sound propagation, the medium must exhibit inertia, enabling its particles to store mechanical energy.
- For sound propagation, the medium must be frictionless, ensuring no energy loss during the transmission of sound.
Ques. Can a sound be heard on the surface of the moon? (2 Marks)
Ans. No, a sound cannot be heard on the surface of the moon. The reason is that there is no atmosphere on the surface of the moon. For sound to propagate, a material medium must be present. Without air or any other gaseous medium sound will not travel. So, it is impossible for sound to travel on the moon. Hence, no sound can be heard on the surface of the moon.
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