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Basic theory of sound

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Seid Adem
Seid Adem

Sound is a vibration that travels in air or other materials as a wave. The speed and wavelength of sound depends on factors like the medium and frequency. Sound is detected when vibrations reach the ear drum and are interpreted by the brain. Characteristics of sound include frequency, wavelength, loudness, quality, and amplitude. Sound can be measured in units like decibels and analyzed to understand acoustics, prevent hearing damage, and improve audio experiences.

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BASIC THEORY OF SOUND Sound is a vibration in an elastic medium such as air, water, building materials and earth. Sound energy progresses in atmospheric pressure and travel a great distance. Sound is the physicalphenomenon that encourages the sense of hearing. It is generated by vibrated bodies in the form of waves of compression and rarefaction in the air. A full circuit by a displaced particle is called a cycles. The time required for one complete cycle is called period and the number of complete cycles per second is the frequency of vibration. Wavelength of Sound: It is the distance a sound wave traveling during one cycle of vibration or wavelength is the distance between adjacent regions where identical conditions of particle displacement occur.
Basic theory of sound
To fine the wavelength of sound in air at a specific frequency by the following equation; 了= Where 了 = wavelength in Feet F = frequency in Hz 1130 = speed of sound feet per second Velocity of Sound: The speed at which the sound travels is called as velocity of sound. Velocity of sound primarily depends on the elasticity and density of the medium. In air, at normal temperature and atmospheric pressure the velocity of sound is approximately 1130 feet per second. Sound may travel at 16,000 ft/s along steel pipes and duct walls. Speed of sound in concrete is about 12,000 ft/s. Some of the important points in sound velocity as follows; These sound waves can travel from source of origin by air in different directions and these sound waves set the ear drum to vibrate then the vibrating ear drum translates by the brain in to sound sensation of hearing.
In humans, hearing takes place whenever vibrations of frequencies from 15 hertz to about 20,000 hertz reach the inner ear. The hertz (Hz) is a unit of frequency equaling one vibration or cycle per second. Sound has the following characters When the sound waves are periodic, regular and long continued, they produce pleasing effect of sound and this sound is also called audible sound. When the sound waves are non-periodic, irregular and very short duration, it produces displeasing effect of sound and this sound is also called audible noise. Sound waves are longitudinal waves and they can move backward and forward along a line in the direction of in which sound is traveling. The velocity of sound depends upon nature and temperature of medium through which it travels. The velocity of sound can be measured by meter per second. See the velocity of sound through different medium given bellow.
Name of the medium Velocity of sound at 200C in m/s Atmospheric air 343 Hydrogen 1305 Nitrogen 338 Pure water 1450 Brick 4300 Concrete 4000 Granite 6400 Glass 5000-6000 Aluminum 5100 Iron 4700-5100 Copper 3900 Brass 3500 Silver 2600 Cork 450-530 Rubber 40-150
Propagation of Sound: When sound is generated in a place, it can move or spread in all direction by air is called as propagation of sound. Sound can propagate for origin to in all directions like a person blowing up a balloon with his moth. See some of the sound propagation principles given bellow; The propagation of sound energy through a media via sound waves i.e. compression and rarefaction of sound waves. The propagation of sound depends up on the frequency of sound source and the capacity of listener ear drum. The propagation of sound depends up on the weather conditions like air temperature, presence of moisture, air velocity etc. The propagation of sound depends up on the topographical features like ground cover, hills and obstacles between the source and receivers, type of space like open or closed.
Diffraction of Sound: The bending of sound waves due to obstacles called as diffraction of sound. Sound diffraction causes decreasing of frequency, loudness, pitch ate. Example if you brought a concert ticket without looking seating arrangement chart. When you enter inside the concert hall your seat will be behind a huge pillar. After starting the film you cannot hear a clear voice due to the obstacle in between you and the music source and because of this the sound wave can bent around the pillar before reaching you. Hearing Sensitivity: The ability of understanding or listening of sound is called as sensitivity of hearing. The hearing of sound depends up on person eardrum, intensity of sound, type of sound tone, distance between the source and the listener, climatic conditions. A healthy young person is capable of hearing sound form about 20Hz to 20,000 Hz. The extent of hearing sensitivity for an individual depends on many factors like age, sex, ethnicity (character of person), previous exposure to high noise level etc.
Physical Character of Sound: The physical characters sound as follows; Frequency Loudness or intensity Quality or timbre. Frequency or Pitch: It is the number of cycle or pressure vibrations produced by a body in unit of time. The greater the number of cycles or vibrations, the higher will be the pitch. The grater the frequency higher the pitch and the lesser the frequency the lower the pitch. Frequency of sound is the measure of the quality of sound. Frequency of sound can be measured in cycles per second or hertz (Hz). A healthy young person is capable for hearing sound energy from about 20 to 20000 Hz.
Loudness or Intensity: It is the flow of wave energy crossing per unit time through unit area. Sound intensities are measured in decibels (dB). For example, the intensity at the threshold of hearing is 0 dB, the intensity of whispering is typically about 10 dB. Sound intensities are arranged on a logarithmic scale due to a wide range of variations of the intensity of sound. Intensity of sound can be calculated by the following equation; I= Where I = sound intensity (w/m2 W = sound power (Watt) d = distance form sound source (m)
Quality or timber: It is the quality of musical note. It is one of the important characters of the sound that allows the ear to differentiate between tones produced by different instruments when the sound waves are identical in aptitude and frequency. Example if a person played a violin, second person played piano and third person a tuning fork, all at the same volume, the tones are identical in frequency and amplitude, but different in quality. From these three sources, the simplest tone is produced by the tuning fork; the sound Because of the acoustical properties of the ear and the resonance properties of the ear's vibrating membrane, however, it is doubtful that a pure tone reaches the inner hearing mechanism in an unmodified form. The principal component of the note produced by the piano or violin also has a frequency of 440 Hz, but these notes also contain components with frequencies that are exact multiples of 440, called overtones, at 880, 1320, and 1760 Hz, for example. The exact intensity of these other components, which are called harmonics, determines the quality, or timbre, of the note.
Amplitude or Volume: Amplitude is the characteristic of sound waves that humans perceive as volume. The amplitude corresponds to the distance that air molecules move back and forth as a sound wave passes through them. As the amount of motion in the molecules is increased, they strike the ear drum with progressively greater force. This causes the ear to perceive a louder sound. This comparison of samples at low, medium, and high amplitudes demonstrates the change in sound caused by altering amplitude. These three waves have the same frequency, and so should sound the same except for a perceptible volume difference. Measurement of sound: Generally sound can measure in terms of pressure level or decibel (dB) and it is used as convent unit to measure the magnitude of sound. By measuring the sound, we can achieve following objects; Sound measurement can helps us to improving of building acoustics and loud speakers and thus improve our enjoyment of music both in concert hall and home; Sound measurement can indicates when sound may causes hearing damage and it helps in taking corrective measures to be avoiding damage;
It permits evaluation of the hearing sensitivity of individuals; It permits the improvement of quality of our daily lives.

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Basic theory of sound

  • 1. BASIC THEORY OF SOUND Sound is a vibration in an elastic medium such as air, water, building materials and earth. Sound energy progresses in atmospheric pressure and travel a great distance. Sound is the physicalphenomenon that encourages the sense of hearing. It is generated by vibrated bodies in the form of waves of compression and rarefaction in the air. A full circuit by a displaced particle is called a cycles. The time required for one complete cycle is called period and the number of complete cycles per second is the frequency of vibration. Wavelength of Sound: It is the distance a sound wave traveling during one cycle of vibration or wavelength is the distance between adjacent regions where identical conditions of particle displacement occur.
  • 3. To fine the wavelength of sound in air at a specific frequency by the following equation; 了= Where 了 = wavelength in Feet F = frequency in Hz 1130 = speed of sound feet per second Velocity of Sound: The speed at which the sound travels is called as velocity of sound. Velocity of sound primarily depends on the elasticity and density of the medium. In air, at normal temperature and atmospheric pressure the velocity of sound is approximately 1130 feet per second. Sound may travel at 16,000 ft/s along steel pipes and duct walls. Speed of sound in concrete is about 12,000 ft/s. Some of the important points in sound velocity as follows; These sound waves can travel from source of origin by air in different directions and these sound waves set the ear drum to vibrate then the vibrating ear drum translates by the brain in to sound sensation of hearing.
  • 4. In humans, hearing takes place whenever vibrations of frequencies from 15 hertz to about 20,000 hertz reach the inner ear. The hertz (Hz) is a unit of frequency equaling one vibration or cycle per second. Sound has the following characters When the sound waves are periodic, regular and long continued, they produce pleasing effect of sound and this sound is also called audible sound. When the sound waves are non-periodic, irregular and very short duration, it produces displeasing effect of sound and this sound is also called audible noise. Sound waves are longitudinal waves and they can move backward and forward along a line in the direction of in which sound is traveling. The velocity of sound depends upon nature and temperature of medium through which it travels. The velocity of sound can be measured by meter per second. See the velocity of sound through different medium given bellow.
  • 5. Name of the medium Velocity of sound at 200C in m/s Atmospheric air 343 Hydrogen 1305 Nitrogen 338 Pure water 1450 Brick 4300 Concrete 4000 Granite 6400 Glass 5000-6000 Aluminum 5100 Iron 4700-5100 Copper 3900 Brass 3500 Silver 2600 Cork 450-530 Rubber 40-150
  • 6. Propagation of Sound: When sound is generated in a place, it can move or spread in all direction by air is called as propagation of sound. Sound can propagate for origin to in all directions like a person blowing up a balloon with his moth. See some of the sound propagation principles given bellow; The propagation of sound energy through a media via sound waves i.e. compression and rarefaction of sound waves. The propagation of sound depends up on the frequency of sound source and the capacity of listener ear drum. The propagation of sound depends up on the weather conditions like air temperature, presence of moisture, air velocity etc. The propagation of sound depends up on the topographical features like ground cover, hills and obstacles between the source and receivers, type of space like open or closed.
  • 7. Diffraction of Sound: The bending of sound waves due to obstacles called as diffraction of sound. Sound diffraction causes decreasing of frequency, loudness, pitch ate. Example if you brought a concert ticket without looking seating arrangement chart. When you enter inside the concert hall your seat will be behind a huge pillar. After starting the film you cannot hear a clear voice due to the obstacle in between you and the music source and because of this the sound wave can bent around the pillar before reaching you. Hearing Sensitivity: The ability of understanding or listening of sound is called as sensitivity of hearing. The hearing of sound depends up on person eardrum, intensity of sound, type of sound tone, distance between the source and the listener, climatic conditions. A healthy young person is capable of hearing sound form about 20Hz to 20,000 Hz. The extent of hearing sensitivity for an individual depends on many factors like age, sex, ethnicity (character of person), previous exposure to high noise level etc.
  • 8. Physical Character of Sound: The physical characters sound as follows; Frequency Loudness or intensity Quality or timbre. Frequency or Pitch: It is the number of cycle or pressure vibrations produced by a body in unit of time. The greater the number of cycles or vibrations, the higher will be the pitch. The grater the frequency higher the pitch and the lesser the frequency the lower the pitch. Frequency of sound is the measure of the quality of sound. Frequency of sound can be measured in cycles per second or hertz (Hz). A healthy young person is capable for hearing sound energy from about 20 to 20000 Hz.
  • 9. Loudness or Intensity: It is the flow of wave energy crossing per unit time through unit area. Sound intensities are measured in decibels (dB). For example, the intensity at the threshold of hearing is 0 dB, the intensity of whispering is typically about 10 dB. Sound intensities are arranged on a logarithmic scale due to a wide range of variations of the intensity of sound. Intensity of sound can be calculated by the following equation; I= Where I = sound intensity (w/m2 W = sound power (Watt) d = distance form sound source (m)
  • 10. Quality or timber: It is the quality of musical note. It is one of the important characters of the sound that allows the ear to differentiate between tones produced by different instruments when the sound waves are identical in aptitude and frequency. Example if a person played a violin, second person played piano and third person a tuning fork, all at the same volume, the tones are identical in frequency and amplitude, but different in quality. From these three sources, the simplest tone is produced by the tuning fork; the sound Because of the acoustical properties of the ear and the resonance properties of the ear's vibrating membrane, however, it is doubtful that a pure tone reaches the inner hearing mechanism in an unmodified form. The principal component of the note produced by the piano or violin also has a frequency of 440 Hz, but these notes also contain components with frequencies that are exact multiples of 440, called overtones, at 880, 1320, and 1760 Hz, for example. The exact intensity of these other components, which are called harmonics, determines the quality, or timbre, of the note.
  • 11. Amplitude or Volume: Amplitude is the characteristic of sound waves that humans perceive as volume. The amplitude corresponds to the distance that air molecules move back and forth as a sound wave passes through them. As the amount of motion in the molecules is increased, they strike the ear drum with progressively greater force. This causes the ear to perceive a louder sound. This comparison of samples at low, medium, and high amplitudes demonstrates the change in sound caused by altering amplitude. These three waves have the same frequency, and so should sound the same except for a perceptible volume difference. Measurement of sound: Generally sound can measure in terms of pressure level or decibel (dB) and it is used as convent unit to measure the magnitude of sound. By measuring the sound, we can achieve following objects; Sound measurement can helps us to improving of building acoustics and loud speakers and thus improve our enjoyment of music both in concert hall and home; Sound measurement can indicates when sound may causes hearing damage and it helps in taking corrective measures to be avoiding damage;
  • 12. It permits evaluation of the hearing sensitivity of individuals; It permits the improvement of quality of our daily lives.