This document discusses key concepts related to sound. It begins by defining sound as vibrations that propagate through a medium as pressure waves that can be heard or sensed. It then discusses the frequency of sound waves, defined as the number of wave cycles per unit of time, with higher frequencies corresponding to higher pitches. Next, it covers wavelength, the distance between consecutive peaks of a sound wave. It also introduces acoustics as the scientific study of mechanical waves, including sound. Finally, it notes that the speed of sound depends on the medium, and was first measured by Newton.

1. SOUND

2. INTRODUCTION
 In physics, sound is a vibration that propagates as a
typically audible mechanical wave of pressure and
displacement, through a medium such as air or water. In
physiology and psychology, sound is the reception of
such waves and their perception by the brain. Sound
can propagate through compressible media such as air,
water and solids as longitudinal waves and also as a
transverse waves in solids (see Longitudinal and
transverse waves, below). The sound waves are
generated by a sound source, such as the vibrating
diaphragm of a stereo speaker. The sound source
creates vibrations in the surrounding medium.

4. FREQUENCY
 Frequency is the number of occurrences of a repeating
event per unit time. It is also referred to as temporal
frequency, which emphasizes the contrast to spatial
frequency and angular frequency. The period is the
duration of one cycle in a repeating event, so the period is
the reciprocal of the frequency. For example, if a newborn
baby's heart beats at a frequency of 120 times a minute, its
period – the interval between beats – is half a second (60
seconds (i.e. a minute) divided by 120 beats). Frequency is
an important parameter used in science and engineering
to specify the rate of oscillatory and vibratory phenomena,
such as mechanical vibrations, audio (sound) signals, radio
waves, and light.

6. WAVE LENGTH
 In physics, the wavelength of a sinusoidal wave is the spatial period
of the wave—the distance over which the wave's shape repeats.[1]
It is usually determined by considering the distance between
consecutive corresponding points of the same phase, such as
crests, troughs, or zero crossings and is a characteristic of both
traveling waves and standing waves, as well as other spatial wave
patterns. Wavelength is commonly designated by the Greek letter
lambda (λ). The concept can also be applied to periodic waves of
non-sinusoidal shape. The term wavelength is also sometimes
applied to modulated waves, and to the sinusoidal envelopes of
modulated waves or waves formed by interference of several
sinusoids. The SI unit of wavelength is the meter.

9. ACOUSTICS
 Acoustics is the interdisciplinary science that
deals with the study of mechanical waves in
gases, liquids, and solids including vibration,
sound, ultrasound, and infrasound. A scientist
who works in the field of acoustics is an
acoustician, while someone working in the field
of acoustical engineering may be called an
acoustical engineer. An audio engineer, on the
other hand is concerned with the recording,
manipulation, mixing, and reproduction of
sound.

10. SPEED OF
SOUND
The speed of sound depends on
the medium that the waves pass
through, and is a fundamental
property of the material. The first
significant effort towards the
measure of the speed of sound
was made by Newton. He believed
that the speed of sound in a
particular substance was equal to
the square root of the pressure
acting on it (STP) divided by its
density.

11. NISCHAY
CLASS 9 B
Chiranjiv
Bharati School
THANK YOU
THE END