Properties of Sound Wave

By: Group 4IV-St.Angela

properties of Sound Waves

• Reflection• Refraction• Diffraction• Interference

• REFLECTION

Reflection

* The return of sound waves from surfaces on which they are incident.

* Reflection of sound waves off of surfaces can

lead to a phenomena called ECHOES *When sound reflects off a special curved surface

called a parabola, it will bounce out in a straight line no matter where it originally hits.

Echoes

• Echoes are the sound of your own voice reflecting back to your ears.

• A sound wave will continue to bounce around a room, or reverberate, until it has lost all its energy.

• A wave has some of its energy absorbed by the objects it hits.

Parabola

• Smooth walls have a tendency to direct sound waves in a specific direction.

• Rough walls tend to diffuse sound, reflecting it in a variety of directions.

Refraction

Refraction

Refraction is the bending of waves when they enter a medium where their speed is different.

Refraction of sound waves is most evident in situations in which the sound wave passes through a medium with gradually varying properties.

• Sound propagates in all directions from a point source. Normally, only that which is initially directed toward the listener can be heard, but refraction can bend sound downward. Normally, only the direct sound is received. But refraction can add some additional sound, effectively amplifying the sound. Natural amplifiers can occur over cool lakes.

Diffraction

Diffraction• The BENDING of waves around small obstacles– The sound with longer wavelength compared to

the obstacle will sound loudest– The amount of diffraction that occurs depends on

both the size of the obstacle and the wavelength of the sound.

The SPREADING OUT of waves beyond small openings - the smaller the gap size then Maximum diffraction

occurs and the sounds spreads out greatly

Spreading Out of Waves• Bigger Gap size Smaller Gap size

Interference

• Is the phenomenon that occurs when two waves meet while traveling along the same medium.

• The interference of waves causes the medium to take on a shape that results from the net effect of the two individual waves upon the particles of the medium.

Constructive Interferene• Occurs at any location along the medium where the two

interfering waves have a displacement in the same direction.

• Both waves have an upward displacement; consequently, the medium has an upward displacement that is greater than the displacement of the two interfering pulses.

• Observed at any location where the two interfering waves are displaced upward. But it is also observed when both interfering waves are displaced downward.

Principle of superposition

• When two waves interfere, the resulting displacement of the medium at any location is the algebraic sum of the displacements of the individual waves at that same location.

RESONANCE

• when one object vibrating at the same natural frequency of a second object forces that second object into vibrational motion.

• The word resonance comes from Latin and means to "resound" - to sound out together with a loud sound.

• It is a common cause of sound production in musical instruments

• .

• *Another example are the woodwind instruments When air is blown through the reed, the reed vibrates producing turbulence with a range of vibrational frequencies , the result of resonance is a big vibration, the reed and air column sound out together to produce a loud sound.

• *Brass instruments involve the blowing of air into a mouthpiece. The vibrations of the lips against the mouthpiece produce a range of frequencies. One of the frequencies in the range of frequencies matches one of the natural frequencies of the air column inside of the brass instrument. This forces the air inside of the column into resonance vibrations. The result of resonance is always a big vibration - that is, a loud sound.

Doppler Effect

• It is an effect produced by a moving source of sound wave

• There is an upward shift in the frequency for the observer being approached by the source

• There is a downward shift for the observer from whom the source is receding

• The Man• - Hears the

sound of the shorter wavelengths

• - Higher frequency

• - Higher pitch

• The Woman• - Hears the

sound of the longer wavelengths

• - Lower frequency

• - Lower pitch

END