Prepared by Bancairen, Karen Mae L. Entong, Jenilyn O. Ramacho, Aileen Q. Violeta, Lean B.

Sound I. The Nature of Waves II. Periodic Waves III. The Speed of Wave on a String IV. The Mathematical Description of a Wave V. The Nature of Sound A. Longitudinal Sound Waves B. The Frequency of a Sound Wave C. The Pressure Amplitude of A Sound Wave  The Speed of Sound A. Gases B. Liquids C. Solid Bars  Sound Intensity  Decibels  The Doppler Effect  Applications of Sound in Medicine  The Sensitivity of Human Ear

I. The Nature of Waves  Water waves have two features common to all waves: 1. A wave is a travelling disturbance. 2. A wave carries energy from place to place.  There are two basic types of Waves: 1. Transverse Wave- is one in which the disturbance occurs perpendicular to the direction of travel of the wave. Radio waves, light waves, and microwaves are transverse waves. 2. Longitudinal Wave- is one in which the disturbance occurs parallel to the line of travel of the wave. A sound wave is a longitudinal wave.

II. Periodic Waves  When waves are consist of cycles or patterns that are produced over and over again by the source, just like transverse and longitudinal, they are called periodic waves.  A wave is a series of many cycles.  Amplitude- is the maximum excursion of a particle of the medium from the particle’s undisturbed position.  Wavelength-is the horizontal length of one cycle of a wave.  Period-is the time required for one complete cycle. Period is related to frequency; f = 1 / T, where period is commonly measured in seconds, while frequency is measured in cycles per second, or Hertz (Hz).

III. The Speed of Wave on a String  The properties of the material or medium through which a wave travels determine the speed of the wave.  Some factors that influences the wave speed: 1. Tension-The greater the tension, the greater the pulling force the particles exert on each other; the faster the wave travels, other things being equal. 2. Mass-For a given net pulling force, a smaller mass has a greater acceleration than a larger mass.  The mass per unit length is called the linear density of a string.  Effects of the tension F, and the mass per unit length are evident in the following expression for the speed v of a small-amplitude wave on a string:

 Typically the wave consists of some disturbance in the medium which depends on space and time. We describe this disturbance as a function. If this function is to describe a travelling wave then the x dependence at time must be a shifted version of the x dependence at time. This means that the x, t dependence must take the form, f takes on a specific value for positions and times satisfying. IV. Mathematical Description of Waves

A. Longitudinal Sound Waves  are waves in which the motion of the individual particles of the medium is in a direction that is parallel to the direction of energy transport. A longitudinal wave can be created in a slinky if the slinky is stretched out in a horizontal direction and the first coils of the slinky are vibrated horizontally. In such a case, each individual coil of the medium is set into vibrational motion in directions parallel to the direction that the energy is transported. V. The Nature of Sound

B. The Frequency of a Sound Wave  Frequency- is the number of cycles per second that passes by a given location.  Pure tone- a sound with a single frequency.  Infrasonic- sound waves with frequencies below 20 Hz.  Ultrasonic- sound waves with frequencies above 20 Hz.  Pitch- frequency detected by ear primarily in terms of subjective quality.

C. The Pressure Amplitude of A Sound Wave  Pressure amplitude is the magnitude of the maximum change in pressure, measured relative to the undisturbed or atmospheric pressure.  Loudness is an attribute of sound that depends primarily on the amplitude of the wave: the larger the amplitude, the louder the sound.

VI. The Speed of Sound A. Gases SubstancesSpeed (m/s) Air ( 0 c)331 Air ( 20 c)343 Carbon dioxide ( 0 c)259 Oxygen ( 0 c)316 Helium ( 0 c)965 B. Liquids SubstancesSpeed (m/s) Chloroform ( 20 c)1004 Ethyl Alcohol ( 20 c)1162 Mercury ( 20 c)1450 Fresh water ( 20 c)1482 Seawater ( 20 c)1522 SubstancesSpeed (m/s) Copper5010 Glass (Pyrex)5640 Lead1960 Steel5960 C. Solids

VII. Sound Intensity Sound Intensity- amount of energy flowing per unit time through a unit area that is perpendicular to the direction in which the sound waves are travelling.

VIII. Decibels Decibels measure the ratio of a given intensity I to the threshold of hearing intensity, so that this threshold takes the value 0 decibels (0 dB). To assess sound loudness, as distinct from an objective intensity measurement, the sensitivity of the ear must be factored in.

IX. The Doppler Effect Doppler Effect  is the change in frequency or pitch of the sound detected by an observer because the sound source and the observer have different velocities with respect to the medium of propagation.

X. Application of Sound in Medicine A. Ultrasound  Used in obstetrics to examine fetus, used to examine some organs, and blood flow  High frequency sound aimed at target  Sound reflects at boundary of tissues with different densities

B. Cavitron Ultra Surgical Aspirator  Used to remove inoperable brain tumors.  Shatters tumor tissue that comes in contact. C. High-Intensity Focused Ultrasound  Sound is focused on a region of the body.  The waves entering the body don’t do damage  Only damage done where focused (like sun and magnifying glass)  The focused energy at target causes heating which kills abnormal cells.

D. Doppler Flow Meter  Transmitter and receiver placed on skin  High frequency sound emitted  Sound reflects off of blood cells  Since cells are moving, Doppler effect exists  Computer can find rate of flow by counting the returned frequency  Used to find areas of narrowed blood vessels

XI. The Sensitivity of Human Ear  The human ear can respond to minute pressure variations in the air if they are in the audible frequency range, roughly 20 Hz - 20 kHz.