Module 1 Part 1.pptx ysbeksjensksmsjsiemwie

Module 1, Part 1
BUILDING SERVICES - IV
WADIYAR CENTRE FOR ARCHITECTURE | MYSURU

Introduction to Sound: Origin and nature of sound, its characteristics and measurement–
Amplitude, frequency, period, wavelength, velocity of sound, sound pressure, sound
intensity, decibel scale, sound and distance – inverse square law.
Humans and Sound: Human hearing, auditory range for humans (Frequency and Intensity
– threshold of audibility and pain), pitch (association with frequency), tone, loudness
(association with amplitude and intensity), Phon.
Module 1, Part 1

INTRODUCTION
• Sound is energy that travels in waves
through elastic media, causing pressure
fluctuations and particle movement.
• It is an auditory experience resulting from
the stimulation of hearing organs due to
pressure changes in media.
• Sound can be reflected, transmitted, or
absorbed by different materials.
• Soft materials like textiles absorb sound
waves, limiting their movement.
• In contrast, hard surfaces, such as ceramic
tiles or wood, reflect sound waves,
creating echoes. The term "reverberation"
describes the reflection of sound waves
off surfaces.
• Dense materials, like concrete, transmit
sound waves through them.

INTRODUCTION
• Sound waves are Longitudinal waves
• In a Longitudinal Wave the particle
displacement is parallel to the
direction of wave propagation.

AMPLITUDE
• The extent of a vibration between the
highest crest to the position of
equilibrium in a propagating wave
motion is called Peak –Amplitude.
• The extent of a vibration between crest
to trough in a propagating wave motion
is called Peak to Peak Amplitude.
• The time needed for one complete
cycle of vibration to pass a given point
is called Time Period.
• Amplitude and sound are directly
proportional, implying that the
amplitude of the wave determines the
loudness of a sound wave.

FREQUENCY
• Frequency describes the number of
complete wave cycles that pass a
fixed point in unit time.
• It is measured in cycles per second
(cps) or hertz unit.
• The distance between two
successive crests or troughs or the
distance of a complete cycle of a
wave propagation in the direction of
wave motion is called wavelength.

VARIATIONS IN
AMPLITUDE,
FREQUENCY &
WAVELENGTH

SOUND WAVE
PROPAGATION
IN AIR

SOUND INTENSITY
• The amount of energy that is transported past a
given area of the medium per unit of time is known
as the intensity of the sound wave.
• The greater the amplitude of vibrations of the
particles of the medium, the greater the rate at
which energy is transported through it, and the
more intense that the sound wave is.
• Intensity is the energy/time/area; and since the
energy/time ratio is equivalent to the quantity power,
intensity is simply the power/area.
• Typical units for expressing the intensity of a sound
wave are W/m2
.
White Cheeked Barbet Call & Song

INVERSE SQUARE LAW
• The mathematical relationship between
intensity and distance is sometimes
referred to as an inverse square
relationship, i.e., the intensity varies
inversely with the square of the
distance from the source.
• The inverse square law states that the
intensity of sound decreases by
approximately 6 dB for each doubling
of distance from the sound source.
• This principle holds true to all energy
sources. The figure to the right seeks to
illustrate it graphically
• The formula to calculate sound intensity
at different points using the inverse
square law is

SOUND PRESSURE
• Sound Pressure is the force of the sound wave (N)
acting on the surface area (m2
) perpendicular to the
direction of the sound.
• Sound is usually measured with microphones
responding proportionally to the sound pressure.
• The lowest sound pressure possible to hear is
approximately 2x10-5
Pa (20 range,, 0.02 mPa) or 2
ten billionths of an atmosphere.
• This minimum audible level occurs normally between
3000 and 4000 Hz.
• For a normal human ear pain is experienced at a
sound pressure of order 60 Pa or 6x10-4
atmospheres.
• Due to this range, it is convenient to express sound
pressure with a logarithmic decibel scale related
typically to the lowest human hearable sound.

DECIBEL SCALE
• The human ear has the ability to handle an immense
range of different sound levels.
• To express sound levels meaningfully in numbers that
are more flexible, a logarithmic scale is used, rather
than a linear one. This scale is called the decibel
scale or dB scale.
• On the decibel scale, 0 dB is the smallest audible
sound.
• A sound 10 times more powerful is 10 dB
• A sound 100 times more powerful than near total
silence is 20 dB
• A sound 1,000 times more powerful than near total
silence is 30 dB
• Sound can be measured with a device called decibel
meter. It measures and samples sound.

THE AUDIBLE SPECTRUM
• Humans are capable of perceiving sounds within a
frequency range of approximately 20 Hz to 20 kHz.
(While infants can hear frequencies a bit above 20
kHz, they tend to lose some sensitivity to high
frequencies as they grow older; for most adults, the
upper limit typically falls between 15 and 17 kHz.)
• The hearing threshold is the sound level below
which a person’s ear is unable to detect any
sound.
• A threshold shift is an increase in the hearing
threshold for a particular sound frequency. It means
that the hearing sensitivity decreases and that it
becomes harder for the listener to detect soft
sounds. Threshold shifts can be temporary or
permanent.
• The human hearing range is a description of the
pitches and loudness levels a person can hear
before feeling discomfort. There are a variety of
sounds in our environment, ranging from faint sounds
like birdsong and rustling leaves to louder sounds like
music, yelling, and industrial noise. This human
hearing range is called the audible range.

PITCH, TONE & LOUDNESS
• Pitch is that characteristic of a musical sound by
which a shrill sound can be distinguished from a
grave one, even though the two sounds may be of
the same intensity
• It is also defined as that characteristic of sound by
which the ear assigns it a place on a musical scale.
• When a stretched string is plucked, a sound of a
certain pitch sensation is produced. If the tension in
the string is increased, the pitch (the shrillness)
becomes higher. Increasing the tension, also
increases the frequency of vibration.
• Therefore, pitch is intimately related to frequency.

PITCH, TONE & LOUDNESS
• Tone is a musical or vocal or a melodious sound
with reference to its pitch, quality, and
strength/intensity.
• A sound of single frequency is called tone; however,
its intensity can vary.
• Two different types of voice tones are as follows:
• Simple tone: a simple tone as we know is a single
frequency sound whose intensity varies accordingly.
• Complex tone: a complex tone is a mixture of several
simple tones, also known as overtones.
• The tone of the lowest frequency is the
fundamental overtone. Additionally, the frequencies
of the overtones can be whole multiples, i.e., 2nd, 3rd,
4th multiple. Therefore, we call these fundamental
frequencies, second, third, and fourth harmonics of the
fundamental tone, itself known as the first harmonic.
• Consequently, a combination of harmonic tones is
pleasant to hear, and therefore, we call it a musical
tone.

Module 1 Part 1.pptx ysbeksjensksmsjsiemwie

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