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are mechanical disturbances that travel through matter. They're characterized by properties like , , and . Understanding these properties helps us grasp how behaves in different media and situations.

Sound waves create alternating regions of and as they move. This process is key to how sound travels and interacts with its environment. We'll explore equations that describe wave propagation and dive into advanced phenomena like and .

Properties and Behavior of Sound Waves

Sound vs hearing distinction

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  • Sound physical phenomenon involves mechanical waves propagating through medium
    • Vibrations create alternating regions of compression and rarefaction (gases, liquids, solids)
  • sensory perception occurs when sound waves interact with ear
    • Ear detects sound waves and converts them into electrical signals
    • Brain interprets signals allowing perception of sound characteristics (pitch, loudness, timbre)

Properties of sound waves

  • Sound waves are
    • Particles in medium oscillate parallel to direction of wave propagation
    • Contrast with transverse waves particles oscillate perpendicular to direction of wave propagation
  • Properties of sound waves include:
    • Frequency (ff) number of oscillations per unit time measured in (Hz)
    • (λ\lambda) distance between two consecutive points in same phase of wave measured in meters (m)
    • maximum displacement of particles from equilibrium position related to loudness of sound
    • Speed (vv) rate at which wave propagates through medium measured in meters per second (m/s)
    • : amount of energy transported by sound waves per unit area per unit time
  • Sound wave behavior in various media:
    • Gases sound waves travel faster in less dense gases and slower in more dense gases (helium vs air)
    • Liquids sound waves generally travel faster than in gases due to closer proximity of particles (water vs air)
    • Solids sound waves travel fastest due to strong intermolecular forces and close packing of particles (steel vs water)

Equations for wave propagation

  • v=fλv = f \lambda
    • Relates speed (vv) frequency (ff) and wavelength (λ\lambda) of wave
    • Calculate any of three variables when other two are known (find wavelength given speed and frequency)
  • in gases v=γRTMv = \sqrt{\frac{\gamma R T}{M}}
    • γ\gamma ratio of specific heats (1.4 for diatomic gases like air)
    • RR universal gas constant (8.314 J/mol·K)
    • TT absolute temperature in kelvins (K)
    • MM molar mass of gas (kg/mol)
  • fo=fsv±vov∓vsf_o = f_s \frac{v \pm v_o}{v \mp v_s}
    • fof_o observed frequency
    • fsf_s source frequency
    • vv speed of sound in medium
    • vov_o speed of observer (positive if moving towards source negative if moving away)
    • vsv_s speed of source (positive if moving away from observer negative if moving towards)

Compression and rarefaction in sound

  • Compression region in sound wave where particles are closer together than equilibrium position
    • Higher pressure and density compared to surrounding medium
  • Rarefaction region in sound wave where particles are farther apart than equilibrium position
    • Lower pressure and density compared to surrounding medium
  • Role in sound transmission:
    1. As sound wave propagates it creates alternating regions of compression and rarefaction
    2. These regions cause pressure variations in medium which transmit sound energy from one point to another
    3. Motion of particles in medium is parallel to direction of wave propagation resulting in longitudinal wave (air molecules in flute)

Advanced Sound Phenomena

  • : study of sound production, transmission, and effects in various environments
  • : amplification of sound waves when driving frequency matches natural frequency of an object or system
  • Interference: interaction of multiple sound waves, resulting in constructive or destructive effects
  • : stationary wave patterns formed by interference of waves traveling in opposite directions
  • : integer multiples of fundamental frequency in a vibrating system, contributing to timbre
  • : logarithmic unit used to measure sound intensity levels relative to a reference intensity

Key Terms to Review (31)

Acoustics: Acoustics is the study of sound, its production, transmission, and effects. It encompasses the physical properties of sound waves, their interaction with various media, and the perception of sound by the human auditory system. Acoustics is a fundamental concept in the study of sound waves, which are central to the topic of 17.1 Sound Waves.
Amplitude: Amplitude is the maximum displacement of a point on a wave from its equilibrium position. It is a measure of the energy carried by the wave.
Amplitude: Amplitude is the maximum displacement or extent of a periodic motion, such as a wave or an oscillation, from its equilibrium position. It represents the magnitude or size of the motion and is a fundamental characteristic of various physical phenomena described in the topics of 1.7 Solving Problems in Physics, 8.4 Potential Energy Diagrams and Stability, 15.1 Simple Harmonic Motion, and beyond.
Compression: Compression is the process of reducing the volume or size of an object or material by applying force or pressure. It involves the act of compressing, squeezing, or pressing something together, resulting in a decrease in its overall dimensions or density.
Compressions: Compressions are regions in a longitudinal wave where the particles of the medium are closest together. They represent areas of high pressure and density.
Decibel: The decibel (dB) is a logarithmic unit used to measure the intensity or power of a sound or other physical quantity. It is commonly used to quantify the relative loudness of sounds and is a fundamental concept in the study of acoustics, sound waves, and sound intensity.
Decibels: Decibels (dB) are a logarithmic unit used to measure sound intensity levels. They express the ratio of a particular sound intensity to a reference level, usually the threshold of hearing.
Doppler effect: The Doppler effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. It is commonly observed with sound waves, where the pitch changes as the source and observer move towards or away from each other.
Doppler Effect: The Doppler effect is the change in the observed frequency or wavelength of a wave due to the relative motion between the source and the observer. This phenomenon is observed in various forms of wave propagation, including sound waves and electromagnetic waves.
Frequency: Frequency is a fundamental concept in physics that describes the number of occurrences of a repeating event or phenomenon per unit of time. It is a crucial parameter in various areas of physics, including wave behavior, oscillations, and sound propagation.
Harmonics: Harmonics are the integer multiples of a fundamental frequency in a standing wave system. They play a crucial role in determining the sound quality and pitch produced by musical instruments.
Harmonics: Harmonics are the natural frequencies of vibration that occur in a system, such as a musical instrument or a sound wave. They are the additional frequencies that are integer multiples of the fundamental frequency, and they contribute to the unique timbre or quality of a sound.
Hearing: Hearing is the perception of sound by detecting vibrations through an organ such as the ear. It involves the conversion of sound waves into electrical signals that are interpreted by the brain.
Hertz: Hertz (Hz) is the unit of frequency, which measures the number of cycles or oscillations that occur per second. It is a fundamental concept in physics, particularly in the study of wave phenomena, such as sound waves and electromagnetic waves.
Interference: Interference is the phenomenon that occurs when two or more waves, such as sound or light waves, interact with each other. This interaction can result in the reinforcement or cancellation of the waves, depending on the relative phases of the waves.
Linear wave equation: The linear wave equation is a second-order partial differential equation that describes the propagation of linear waves, such as sound or light waves, in a medium. It is typically written as $\frac{\partial^2 u}{\partial t^2} = c^2 \nabla^2 u$, where $u$ represents the wave function and $c$ is the speed of the wave.
Longitudinal Waves: Longitudinal waves are a type of wave in which the displacement of the medium is parallel to the direction of wave propagation. This means the particles in the medium oscillate back and forth in the same direction as the wave is traveling.
Rarefaction: Rarefaction refers to the region in a sound wave where the particles of the medium are spread apart, resulting in a decrease in pressure and density compared to the surrounding areas. This phenomenon is a crucial aspect of the propagation of sound waves.
Rarefactions: Rarefactions are regions in a longitudinal wave where the particles are spread apart, resulting in a decrease in pressure and density. They occur between compressions, which are regions of high pressure and density.
Resonance: Resonance occurs when a system is driven at its natural frequency, leading to a significant increase in amplitude. It is a crucial concept in oscillations and wave phenomena.
Resonance: Resonance is a phenomenon that occurs when a system is driven by a force that matches the system's natural frequency of oscillation, leading to a significant increase in the amplitude of the system's response. This concept is fundamental across various fields in physics, including mechanics, acoustics, and electromagnetism.
Sound: Sound is a mechanical wave that propagates through a medium such as air, water, or solids by the vibration of particles. It is characterized by properties such as frequency, wavelength, amplitude, and speed.
Sound Intensity: Sound intensity is a measure of the amount of energy carried by a sound wave per unit area perpendicular to the direction of propagation. It represents the power of the sound wave and is an important factor in understanding the characteristics and effects of sound.
Sound intensity level: Sound intensity level is a logarithmic measure of the sound intensity relative to a reference value, typically measured in decibels (dB). It quantifies how loud a sound is perceived.
Sound Waves: Sound waves are the vibrations that travel through a medium, such as air or water, and carry energy from one location to another. These waves are created by the oscillation of particles in the medium, which causes the pressure and density of the medium to fluctuate, resulting in the propagation of the sound wave.
Speed of Sound: The speed of sound is the distance traveled by a sound wave per unit of time. It is the rate at which sound waves propagate through a medium, such as air, water, or a solid material. The speed of sound is an important concept in the study of sound waves and their behavior.
Standing waves: Standing waves are wave patterns that result from the interference of two waves traveling in opposite directions, creating nodes and antinodes. These waves appear to be stationary and do not propagate through the medium.
Standing Waves: Standing waves are a pattern of waves formed by the interference of two waves traveling in opposite directions. They are characterized by regions of constructive and destructive interference, resulting in stationary points of maximum and minimum amplitude along the medium.
Wave Equation: The wave equation is a fundamental mathematical equation that describes the propagation of waves, such as sound waves, light waves, and waves on a string. It governs the relationship between the displacement of a wave and the variables that determine its behavior, including time, position, and the properties of the medium through which the wave is traveling.
Wavelength: Wavelength is the distance between successive crests or troughs of a wave. It is typically represented by the Greek letter lambda ($\lambda$).
Wavelength: Wavelength is a fundamental characteristic of waves, representing the distance between consecutive peaks or troughs of a wave. It is a crucial parameter that describes the spatial properties of various wave phenomena, including light, sound, and other types of oscillations.
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Glossary
Glossary
17.2 Speed of Sound