Application of Sound waves
MUSICAL INSTRUMENTS
Subject: Physics
Theme: Waves-Motion Without Material Transfer
Topic: Application of Sound waves
Sub Topic:
Date: dd/mm/yyyy
Class: S.S.S 2
Duration: 40 Minutes
No of Learners: 40
Learning Objectives: By the end of the lesson learners should be able to:
1. List and explain the application of sound wave
Sound wave is applicable in musical instrument. There are three classes of musical instrument:I. Wind instruments: Wind instruments are instruments that make sound through a vibrating column of air. Examples are flutes, trumpets, saxophone, etc. Wind instruments can either be of open or closed pipes. A player blows through the open end causing a column of air to vibrate thereby producing sound. by manipulating the keys of the instrument, the length of the vibrating column in the instrument is altered and as a result sound of different tones, frequencies or pitches are produced. For closed pipes, adjustable or movable piston may be fixed at the close end. In some cases, a vibrating read is used to produce different vibrations at the mount of the player.
II. Stringed instrument: Examples of string instruments are guitar, piano, sonometer, violin etc. String instruments work on the principle of vibrating string with reference to frequency, in other words the frequency of a vibrating string depends on the length of the string, density of the string and the tension in the string. a long, thick and lose string produces a low frequency sound. While a short, thin and taut string produces high frequency sound. The various combination of the fundamental frequencies and overtones produce sounds of various quality.
III. Percussion instrument: They produce sound when hit or struck. They have taut skin, membranes, rods, which vibrate when struck. they produce notes which are usually of short duration. examples are talking drum, bells, xylophone, tuning fork, etc. For a drum for instance, it is made up of a stretched membrane. The cords around the edge help in increasing the pitch. same goes for the other percussion instruments.
2. Defined Hearing and Hearing Aid
Hearing: is the sense concerned with the perception of sound. We hear with the ear and see with the Eye.As with the eye, the ear may also have some defects or impairments.Just as we need spectacles or eye - glasses to improve, or enhance our ability to see very clearly, we also do need hearing aids to hear more loudly and distinctly.
Hearing Aid: is a device used by a person with impaired or defective hearing ability to improve his or her ability to hear properly. The device increases the loudness of sound in the ear of the wearer. This sense of hearing depends on the ability of the listener to detect the pressure of sound waves in the air around him or her. The hearing aid helps the listener by acting as an amplifier. It does so by increasing the pressure of sound waves and delivering it into the ear at a point within the ear canal.
3. List and explain Types of hearing aids
There are two principal types of hearing aids. These area.) Air-conduction Aids:
An air-conduction aid amplifies sound and brings it directly into the ear. This is the hearing aid most people wear.b.) bone-conduction aids:
The bone conduction aids are for these people in whom sound cannot be transmitted through the outer or middle ear. This type of aid therefore brings sound waves to the bony parts of the head behind the ear. The bone transmits the air vibrations to the auditory nerves of the cochlea Hearing becomes possible when these nerves are stimulated.4. List and explain Parts of hearing aids:
Modern hearing aids are electronically operated.They are made up of five major parts:(1) The Microphone, that picks up the sound and changes it into electrical signals.
2) the Amplifier that increases the strength of the signals.
3) A Receiver or ear-piece that changes the signals back to amplified sound that can be understood by the listener.
(4) The Battery which supplies power for the operation of the equipment.
(5) The ear-mold that secures the receiver in the ear canal.
Rationale:
Sound is a form of energy produced by vibrating bodies, as a result, every object that can vibrate is a source of sound. Musical instruments are sources of sound as they are set into vibration when plucked, struck or blown. Standing waves are produced in them and they vibrate at their natural frequency.Prerequisite/ Previous knowledge:
Application of light wave, musical nstrumentsetc.Learning Materials:
Tunning fork, guitar strings, drumheads, and tuning fork, vocal cords.Reference Materials:
1. New School Physic for Senior Secondary Schools, by M. W. Anyakowa.2. Lamlas's SSCE and UTME, by O. Ajaja and H. B. Olaniyi.
3. Okeke P.N and etal (2011), Macminian, Senior Secondary School Physics, New Edition.
4. Farinde E.O and etal (2015), Essential Physics. 6th Edition,
5. New System Physics by Dr. Charles Chow.
Lesson Development:
| STAGE | TEACHER'S ACTIVITY | LEARNER'S ACTIVITY | LEARNING POINTS |
|---|---|---|---|
| STEP I: PREVIOUS KNOWLEDGE full class session |
The teacher asks learners questions based on previous knowledge. Differences between sound and light waves. |
Learners' response to teacher's question. 1. Sound waves is longitudinal wave while Light wavves is transverse wave. 2. Sound waves cannot travel through vacuum (free space) while Light waves can travel through vacuum (free space) 3. Sound waves travel with a speed of 330-340 m/s while Light waves travels with the speed of light 3X10⁸ m/s Soubd waves has a long wavelength while Light waves has a short wave length 4. Sound waves is mechanical in nature while Light waves is electromagnetic in nature |
Confirming previous knowledge. |
| STEP II: INTRODUCTION full class session |
The teacher introduce the topic for discussion. Clarinets, flute, saxophone, trumpet are examples of wind musical instruments. A musical note originates from a source vibrating in a uniform manner with one or more constant frequencies music is a combination of musical notes. All wind instrument use resonating air columns to produce their sounds. Sounds from wind instruments may originate from The guitar, the sonometer and piano are examples of stringed musical instruments. These instruments may be set in vibration by a bow, or plucked with a finger e.g. a violin is bowed while a guitar is plucked. The frequency of a vibrating string depends on its length, the mass and the force that keeps the string taut. Stringed instruments vibrate as a whole and in loops at the same time e.g. the violin. These vibrations produce both the fundamental and overtones frequencies. (drums, bell, talking drum) Percussion instruments produce musical notes when they are struck or hit. They have rods, plates or membranes that vibrate when struck; for example, there are rods in bells, plates (bars) in xylophones and membrane in drums. |
Learners listen to teacher, ask questions and make contribution. | Developing the idea of the topic. |
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| STEP III: EXPLORATION Grouping |
The teacher presents the instructional material to the students and divides them into four groups. The representative of a group is asked to discuss the uses of the material. Aim is to show Propagation of sound waves in air. HINT: Sound is a form of energy produced by vibrating bodies. For example, when we strike a body such as a tuning fork its prongs vibrate, the vibrations give rise to sound waves. Therefore, sound waves are produced by vibrating bodies as a result every object that vibrates is a source of sound. Examples are chairs, iron, drums, air column e.t.c. almost any object can vibrate and hence a source of sound. The teacher asks the students to strike the tunning fork against their desks place very to their hears and state their observations. The teacher leads the students into the discussion from the observations gathered from the exploration, the Students equally gives their contribution's and the teacher gives the students note on the topic. |
Learners' expected answer The students carry out the instructions accordingly and state their observations. A material medium is required for sound to be transmitted or else sound will not be transmitted from the source to the hearer. Sound cannot travel through a vacuum as light does. Sound waves are transmitted in air by the displacement (vibrations) of air molecules in longitudinal form as earlier discussed. Sound is also transmitted through liquids and solids. Sound does not readily travel from one medium to another due to the different densities of the media. For example, the heartbeat of a man is not heard by listening in the air close to his chest but by putting ones ear directly on his chest( a solid of similar density) or a stethoscope(connected to the listeners ear) to touch the mans chest. |
Sound is transmitted through gases, plasma, and liquids as longitudinal waves, also called compression waves. It requires a medium to propagate. |
| STEP IV: DISCUSSION | The teacher explain vibration in pipe and guides the students to list and explain the characteristics of sound waves. Sounds are produced when an air column in a pipe is set into vibration an external disturbance from one end of it with the other end opened or closed. The type of sound waves produced in a stationary longitudinal wave. In an open pipe, the other end is an antinode, while in a closed pipe the other end is a node. The frequency of vibration of air in these pipes increases as the length of air column decreases. If (f) is frequency and(L) is length of air, then f is inversely proportional to L Usually we can vary the length of air column either by shortening the tube or by filling it with water and gradually running off water to create more space for air. The Teacher tells the students that vibration in pipes are used in flutes and other musical instruments. |
The students listed and explained the characteristics of waves: A. PITCH: This depends on the frequency of the sound waves. If the frequency is increase, the pitch of the sound also increases. B. LOUDNESS: The loudness of the sound depends on its intensity. The intensity of the sound of the wave is the rate of the flow of energy per unit area, perpendicular to the direction of the wave. Intensity is proportional to the square of the amplitude. The greater the intensity, the louder the sound. C. QUALITY: This is the property which enables us to distinguish the same note played on different instruments e.g a piano and an organ, the quality of a musical notes depends on the harmonies. When a note is produced, the strongest, audible frequency heard is the fundamental. All other frequencies present ar harmonics or overtones. |
Characteristics of sound waves. |
| The teacher guides students to explain the three classes of musical instrument | The students explain the classification of musical instruments: I. Wind instrument: wind instruments make sound, through a vibrating column of air. The air is set into vibration when the player blows the open end. Examples are: flutes, trumpets, pipe organ, clarinets and saxophones. II. Stringed instrument: In string instruments, the frequency of the vibrating string depends on length of string, mass per unit length of string and tension in string. The vibration of the string produces fundamental frequency and overtone which combine to make music. A long thick wire or string produces a low frequency note, while short thin and taut string produces both the fundamental frequency and the overtones. The various combination of the fundamental frequency and the overtones produce musical sounds of various quality. Examples of stringed instrument are: guitars, sonometer, piano, violin etc. III. Percussion instrument: these are instruments which produces sound when their surface is hit. The surface vibrate when hit. They produce a musical note of short duration. Examples are: drums, bells, gongs, xylophones, tuning forks etc. |
Classification of musical instuments | |
| The teacher explains the relationship between frequency and (1) Tension (2) mass per unit length and (3) length of the string. Using the sonometer. The sonometer is an instrument with which the frequency of a note produced by a plucked string can be studied. It consists of a hollow sounding box, along whose length is a string stretched. The string is attached to a peg at one end and the free end is passed over a grooved smooth pulley. To the free end, is an attached weight by which the string is stretched taut. Two moveable knife edges function as fixed ends and as well used to vary the length of the string between the fixed ends. The weight, W. equals the tension T in the string. When the weight (Tension) in the string is kept constant, and length are varied, the relationship below is obtained. f α 1/L The shorter the length, the higher the frequency When the length is kept constant and the frequency and tension are varied then we have: f α √T The higher the tension, the higher the frequency. When both the length of the string and the tension are kept constant and strings of different mass per unit length are used with varying frequencies then: f α 1/√m The smaller the mass per unit length (thickness) the higher the frequency. The varying frequencies are obtained with the help of tuning forks of known frequencies. When the three relationships above are combined, it gives f α 1/l√T/m therefore f = k/l(√T/m) Where: f = frequency of vibration of string L = length of string T = tension in the string m = mass per unit length of string k is a constant which depends on the mode of vibration (number of loops) Therefore fo = 1/2L√T/m F1 = 2fo = 1/L√T/m F2 = 3fo = 3/2L√(T/m) and so on. |
The Students gives their contribution's based on their Understanding. | Vibration in pipe | |
| STEP V: APPLICATION | The teacher guides learners to explain resonance and force vibration Compare resonance to a playground swing. Pushing the swing at its natural frequency makes it go higher and higher. Similarly, resonance occurs when an object is exposed to its natural frequency, causing it to vibrate more strongly. Resonance is the reinforcement or amplification of vibrations when an object is exposed to its natural frequency. Imagine a glass filled with water as a musical instrument. When you tap it lightly, it produces a sound. Tapping it with the right frequency creates resonance, making the sound louder. So, just as a swing goes higher when pushed at its natural frequency, objects resonate more strongly when exposed to their natural frequencies. Force vibration explains how external forces induce vibrations and influence sound production. Force vibration is about inducing vibrations in an object through external forces, affecting various sound characteristics or deals with the initiation of vibrations through external forces, while resonance involves the enhancement of vibrations when the applied force matches the natural frequency of an object. It focuses on the reinforcement or amplification of vibrations when an object is exposed to its natural frequency, leading to a stronger and more sustained sound. The teacher leads the students into the discussion from the observations gathered from the exploration, the Students equally gives their contribution's and the teacher gives the students note on the topic. |
The students listen to teacher, ask questions and make contribution. Force vibration is the induction of vibrations in an object due to an external force acting upon it and they can result in the generation of sound waves. Examples of force vibrations in everyday life includes plucking a guitar string, striking a drumhead, or speaking into a microphone. In the class, we stuck the tuning fork and then while it vibrated, we placed it on the table. Did you remember how the table produced sound higher than the tuning fork? That is an example of forced vibration. A glass producing a loud sound when tapped with a spoon? The idea that this phenomenon is related to is what we refer to as Resonance. All types of vibrating systems have their own natural frequency of vibration.This is the frequency with which the body or system will vibrate when it is left undisturbed after being set into oscillatory motion. For example the natural frequency(f) of a simple pendulum at any place depends on the length of the pendulum according to the relation. T = 2π√L/g where T = 1/f If a vibrating body is placed in contact with another body, the latter will also be forced to vibrate at the same frequency with the former. The vibration of the second body is called a forced vibration. |
Force Vibration are those vibration that result from an external periodic force acting on a system and setting the system vibrating at the same frequency as the external periodic force. Such vibrating body usually has its own amplitude of vibration greatly reduced by air resistance. This process of reduction is called DAMPING. Example, the setting of a table to vibrate when a vibrating tuning fork is placed on it. |
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| STEP VI: EVALUATION | The teacher asks the learners questions. 1. Why do we see a flash of lightning before the accompany sound of thunder? 2. List and explain the characteristics of sound waves. 3. Why are sound waves called mechanical waves? 4. In which medium does the sound wave travel the fastest? 5. In which medium is the speed of sound the lowest? 6. What is the frequency of a sound wave? 7. What is the reverberation of sound? |
The learners expected answers. 1. We see a flash of lightning before the accompany sound of thunder because the velocity of light is about (v = 3X10⁸ m/s) is far greater than the velocity of sound about (330 m/s). Thus suppose we hear the sound of thunder 10 seconds after we have seen the lighting flash then the distance between us and the storm center or the point of the lighting and thunder is giving by S = Vt S = (300 X 10)m S = 33km. 2. The characteristics of sound waves include the following (a) Pitch: The pitch of a note is its position on the musical scale it is a characteristic of a note which enables one to differentiate a high note from a low pitch and the left hands side keys produce note of low pitch. (b) Loudness and Intensity: I. Intensity of sound is the rate of low of energy per second per unit area perpendicular to the direction of propagation of the sound wave. II. Loudness is the magnitude of the sensation resulting from a sound reaching the ear. (c) Quality or tone (timber): Quality is a characteristic of a note of a musical instrument which distinguishes it from another note of the same pitch and loudness produced by another instrument. 3. Mechanical waves are waves that require a medium to transport their energy from one location to another. Sound is a mechanical wave and cannot travel through a vacuum. 4. The sound waves travel the fastest through solids. 5. The speed of sound is lowest in gases. 6.The number of rarefactions and compressions that occur per unit of time is known as the frequency of a sound wave. 7. If the area is large and has multiple reflecting surfaces such as valleys and huge empty rooms, we hear multiple echoes from a source of sound and we call this phenomenon reverberation. |
Ask the learners questions to assess the achievement of the set objectives. |
| CONCLUSION | The teacher concluded the lesson with the students. Almost any object can vibrate and hence be a source of sound; we can demonstrate the production of sound in the laboratory using a tuning fork two steel prong which vibrate when struck with a hard rubber giving some sound. An important aspect of sound transmission is that a material medium is always required for the passage of sound can be demonstrated with an apparatus that consists of an electric bell covered with a bell jar placed on the plate of a vacuum pump. The clapper is still seen to be vibrate even through no sound is heard, showing that sound waves cannot travel through vacuum.RESONANCE IN STRINGS: Stationary waves can occur on a stretched string or wire. This is obtained by varying the driving frequency of the string. |
The students listen and make contribute | Transmission of sound |
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| ASSIGNMENT | The teacher gives learners a take home. | 1. The speed of sound travelling in various media increases in the following correct order: (A) iron bar, air, water (B) iron bar, water, air (C) air, water, iron bar (D) water, iron bar, air (E) water, air, iron bar. 2. Which of the following determine(s) the frequency of vibration of a stretched string? I. The length of the string II. The density of the material of the string III. The tension in the string (A) I only (B) II only (C) III only (D) I and Il only (E) I, II and Ill. 3. Sound waves differ from water wave in that (A) energy transfer is involved (B) they can be refracted and reflected (C) no transfer of the medium is involved (D) they are longitudinal waves (E) they involve vibration. 4. A sounding tuning fork is brought near the end of a pipe containing an air column and the loudness of the sound increases. This effect is due: (A) diffraction (B) an echo (C) resonance (D) interference (E) reverberation. 5. which of the following statements is/are not true: (A) The velocity of sound in air does not A depend on its intensity (B) The velocity of sound in air does not depend on the temperature. (C) sounds travel faster through a solid than through a gas (D) Sound does not require a material medium for transmission. (E) The pitch of sound depends on its frequency. 6. What change(s) is/are observed in the sound produced by a siren when the speed of revolution is increased? I. The pitch become higher II. The wavelength of sound increases III The velocity remains constant. (A) I only (B) II only (C) III only (D) I and II only (E) I and III only. 7. In a stringed instrument like a guitar or violin, high pitched notes are produced by strings that are: (A) thin and short (B) thick and short (C) thin and long (D) thick and long (E) none of the above 8. When the length of a vibrating string is tripled, its frequency of vibration: (A) becomes six times the former value (B) becomes one-third its former value (C) becomes three times its former value (D) becomes one-sixth the former value (E) remains the same. 9. Which of the following slatement(s) is/are false? (A) In a flute, the air column In set into vibration by an air jet. (B) In the reed-type organ pipe, the air column is caused to vibrate by the vibration of the reed, (C) An open organ pipe will resonate to all harmonics. (D) In a woodwind instrument such as flute, the effective length of the air column cannot be altered. (E) In an instrument such as a trumpet, the vibrating air column is caused by the vibration of the player's lips. 10. Explain: (i) Why one is able to distinguish betwet a note produced by a violin and a guitar (ii) Why thunder is usually heard some seconds after a flash of lightning is seen (iii) How the depth of a seabed can be determined using the properties of sound (iv) The possible causes of poor acoustics in a concert hall and how one can rectify these. |
Improving their level of understanding on application of sound waves. |