Acoustic Physics: Sound Wave Properties and Phenomena
Acoustic Physics: Sound Wave Properties
Elongation: The distance between the point of balance and the position of particles at a given time.
Amplitude: The distance between the highest point and the point of equilibrium, similar to elongation. (Higher energy results in greater amplitude)
Period: The time it takes a particle to complete one vibration.
Frequency: The number of times an event is repeated within a given time. Specifically, the number of vibrations performed in 1 second.
Wavelength: The distance from one point on a wave to the corresponding point on the next wave.
Propagation Speed: The speed at which a sound wave travels (approximately 340 m/s).
Infrasound: Sound waves with frequencies below 20 Hz.
Ultrasound: Sound waves with frequencies above 20,000 Hz.
Reflection: The bouncing of sound waves off a surface. Sound reflects more effectively off compact solids.
Incident Sound: The sound wave that travels toward an obstacle.
Reflected Sound: The sound wave that is returned after colliding with an obstacle.
Normal Line: An imaginary line that runs perpendicular to the obstacle, used to measure angles of incidence and reflection.
Absorption: The process by which an obstacle captures the energy of a sound wave.
Transmission: The passage of sound waves through an obstacle.
Refraction: The bending of sound waves due to variations in air temperature.
Diffraction: The bending of sound waves around obstacles or through openings. More pronounced in bass frequencies due to their longer wavelengths. Occurs when a sound passes through an opening and expands as if it were produced at the opening itself. The opening should be equal to or smaller than the wavelength.
Echo: The repetition of a sound caused by reflection.
Reverberation: The persistence of sound in a space after the original sound has stopped, caused by multiple reflections, especially in small places (less than 17 m).
Compression Zone: Occurs only in longitudinal waves, where there is a high density of molecules.
Rarefaction Area: Occurs only in longitudinal waves, where there is a low density of molecules.
Elasticity: The ability of an object to return to its original shape after being deformed. Higher density generally means less elasticity.
Interference: The phenomenon that occurs when two or more waves arrive simultaneously at one point, resulting in either addition or cancellation of the waves.
Constructive Interference: When the resulting wave has a larger amplitude than the original waves, producing a sound of greater intensity.
Destructive Interference: When the resulting wave has a smaller amplitude than the original waves, potentially resulting in silence or reduced sound.
Compound Sounds: Sounds that are made up of multiple frequencies and pure tones. They are the sum of pure sounds.
Pure Sounds: Sounds consisting of a single frequency. Example: a tuning fork.
Timbre: The unique quality of a sound, determined by the combination of all the frequencies and overtones present in an instrument or pure sound.
White Sound: A sound that contains all audible frequencies at equal intensity.
Natural Frequency: The frequency at which an object vibrates most easily, determined by its mass and shape. (Greater mass results in lower frequency)
Forced Vibration: When a vibrating body causes another body to vibrate.
Resonance: Occurs when two objects have the same natural frequency and one vibrates in response to the other, causing an increase in amplitude.
Doppler Effect: The change in frequency of a wave in relation to an observer who is moving relative to the wave source. The speed of the sound source is less than the wave velocity (340 m/s). The wavelength is shorter on the side towards which the sound source is moving and longer on the opposite side. As the sound source approaches, the frequency increases, resulting in a higher pitch.
Bow Wave: A phenomenon related to the Doppler effect that occurs when the speed of a sound source exceeds the speed of sound (+340 m/s). The amplitude is larger, and constructive interference occurs.
Sonic Boom: The loud sound heard when the edge of a bow wave reaches an observer’s ear, caused by a wave with a very large amplitude.
Shock Wave: A pressure wave produced by an object traveling at or above the speed of sound, creating a compression zone in front and a rarefaction zone behind. These zones propagate through the air, resulting in a very loud sound.
Low-Pitched Sound: A sound with a low frequency.
High-Pitched Sound: A sound with a high frequency.