Waves: Sound and Hearing Study Guide

This lesson is part of the King's InterHigh Science Explore 1 curriculum, focusing on 'Waves'.
Current Topic (Week 21): Sound and Hearing.
Curriculum Progression: - Last Week: Colour. - Next Week: The Earth.
Defined Learning Objectives: - Identify that sound is produced by vibrations and propagates as waves through a medium. - State and utilize appropriate scientific terms to describe the specific features of a sound wave. - Understand the biological and physical mechanisms of hearing and successfully label the anatomy of the human ear.
Recommended Textbook Reference: CGP Key Stage Three Science, Higher Level Complete Revision & Practice (Title: Waves, Pages 136–150).

The loudness or intensity of sound is measured in units called decibels ( $dB$ ).
Representative levels of sound for various activities: - $0\,dB$ : Silence (threshold of hearing). - $20\,dB$ : Leaves rustling. - $40\,dB$ : Whispering. - $60\,dB$ : Normal speech. - $80\,dB$ : Heavy traffic. - $100\,dB$ : A jet taking off.

Sound Origin: Sound is fundamentally caused by vibrations. If a vibrating object, such as a struck tuning fork, is covered with a pillow, the sound is muffled or silenced because the pillow absorbs the vibrations and prevents them from moving through the air medium.
Amplitude: Defines the volume or loudness of a sound wave. - A larger amplitude results in a taller wave, which corresponds to a louder sound.
Frequency: The number of sound waves passing a specific point per second. - It is measured in Hertz ( $Hz$ ). - In a speaker simulation, increasing the frequency increases the speed/rapidity of the speaker's movement. - In a speaker simulation, increasing the amplitude increases the distance of the speaker's movement (the physical displacement).
Pitch: Describes how high or low a sound is. - Pitch is directly determined by frequency (vibrations per second). - High Frequency = High Pitch. - Low Frequency = Low Pitch.

Sound waves consist of specific regions based on particle density: - Compression: A region where particles are pushed together. - Rarefaction: A region where particles are spread apart.
Wavelength Definitions: - Compression Wavelength: The distance measured between two consecutive compressions. - Rarefaction Wavelength: The distance measured between two consecutive rarefactions.
Zero Point: A set of points in the wave model where the amplitude is exactly zero.

In a visual comparison of sound waves (labeled A, B, C, and D): - Loudness/Volume: Sound waves A and D have the same loudness/volume (identical peak amplitude). - Highest Frequency: Sound wave C possesses the highest frequency (most waves per unit of space/time). - Lowest Frequency: Sound wave A possesses the lowest frequency. - Lowest Pitch: Sound wave A has the lowest pitch, as it has the lowest frequency.

Scenario: Sheila wrapped a ticking clock in varying layers of bubble wrap (one, two, and three layers) and measured the audible volume from a distance of $1\,metre$ .
Research Question: How does the thickness of bubble wrap affect the audible volume of the ticking of an alarm clock?
Hypothesis/Prediction: As the thickness of the bubble wrap increases, the audible volume of the ticking will decrease.
Measurement Equipment: The ideal piece of equipment for this investigation is a decibel meter.
Control Variables: Factors that must be kept constant to ensure a fair test include: - The specific method used to measure the volume. - The distance between the clock and the decibel meter ( $1\,metre$ ). - The specific type of bubble wrap used. - Background noise levels from the external environment.

Definition: Ultrasound consists of sound waves with a frequency exceeding $20000\,Hz$ . This frequency range is beyond the upper limit of human hearing.
Applications of Ultrasound: - Soft Tissue Scans: Used to create images of internal body structures; most commonly used in prenatal scanning to observe and measure a developing baby. - Cleaning: Used to clean delicate or intricate objects by vibrating a liquid, which physically knocks dirt off the surfaces. - Medical Treatment: Used to treat damaged muscles by stimulating increased blood flow to the affected area. - Echolocation: Biological and technological systems use ultrasound waves for navigation and object detection.

Anatomical Components: - Pinna: The outer ear structure that catches sound waves. - Ear Drum (Tympanic Membrane): Converts sound waves into mechanical vibrations. - Ossicles: Small bones in the middle ear comprising the Hammer, Anvil, and Stirrup. - Cochlea: Contains tiny hairs that vibrate in response to mechanical energy. - Auditory Nerve: Carries electrical messages/signals from the ear to the brain.
The Step-by-Step Process of Hearing: 1. A source (e.g., a tuning fork) vibrates. 2. The vibrations from the source are transferred to the surrounding air particles. 3. The air particles vibrate, carrying the energy as a wave. 4. The vibrations reach the ear, causing the ear drum to vibrate. 5. The ear drum passes these vibrations to the ear bones (ossicles), which then vibrate. 6. The vibrations move into the inner ear, causing hairs within the cochlea to vibrate. 7. A signal/message is sent to the brain via the auditory nerve for interpretation.