Understanding Sound: Properties, Transmission, and Reflection

Understanding Sound: Properties and Behavior

Sound is produced by the vibration of an elastic medium, which can exist in three states (solid, liquid, gas).

An elastic medium possesses the ability to regain its original shape after deformation.

Types of Sound

The sounds audible to the human ear have frequencies between 20 Hz and 20,000 Hz.

• Infrasound: Sounds below 20 Hz.
• Ultrasound: Sounds above 20,000 Hz.

Sound is a longitudinal mechanical wave where the medium undergoes vibrating pressure variations. Key aspects include:

• Compression: High-pressure zone.
• Rarefaction: Lower-pressure zone.

Sound Intensity and Volume

The intensity of a sound wave is a physical quantity defined as the sound energy carried by the wave per unit time through a unit area. It is measured in [units].

Sound intensity is related to volume. A sound of 10 dB is 10 times more intense than one of 0 dB.

Tone (Pitch)

Tone is related to frequency. Lower frequencies (slow vibrations) produce bass sounds, and higher frequencies (fast vibrations) produce high-pitched sounds.

High-frequency sounds at high intensity are more harmful than bass sounds. Dangerous sound levels can damage the inner ear and affect the function of the middle ear muscles.

Timbre (Sound Quality)

Timbre differentiates between two sounds of equal pitch and loudness, emitted by two different sound sources. The timbre is related to its source.

Sound Transmission (Propagation)

The speed of sound transmission depends on three factors:

1. Density of the medium.
2. Elasticity: The ability of the medium to recover its original shape.
3. Medium temperature.

Sound Transmission in a Vibrating String

The speed of sound in a vibrating string depends on:

1. Tension of the string (measured in Newtons, N).
2. Length of the string (measured in meters).
3. Mass of the string (measured in kilograms).

Sound Reflection

Sometimes, an echo occurs when sound is reflected in a denser medium and reaches the ear of a person with a time difference of less than 0.1 seconds.

Sound Reverberation

Reverberation involves multiple sound reflections, leading to interference.

Sound Refraction

Refraction occurs when sound passes from one medium to another, causing a deviation of the wave related to the speed of propagation in each medium. Sound transmits best through layers of cold air.

Sound Diffraction

Sound waves bend around obstacles and continue to spread. Sound has the ability to circumvent obstacles.

Sound Absorption

Sound absorption is related to the energy-absorbing and reflective properties of a material.

Resonance

Every body has its own natural frequency. The resonance phenomenon occurs when the forcing frequency on an object equals its natural frequency, causing an increase in amplitude. The natural frequencies are those where the minimum energy is needed to produce forced vibrations. The natural frequency depends on the elasticity and shape of the object.