This focus idea is explored through:
Contrasting student and scientific views
Student everyday experiences
Many young children’s opinions on sound suggest that they do not think too deeply about their experiences with sound or hearing and frequently take their experiences for granted. The few opinions they do have vary greatly.
Some children believe that sound is actually a physical ‘substance’ that is made of particles or something similar. They believe sound acts as a sort of ‘wind’ that moves around. A smaller number of children do not associate the detection of sound with the act of hearing or the function of their ears. Some do recognise that their ears play a role in hearing sounds but they believe that only the outer visible ear structure is somehow involved and that their inner ear and brain play no part in the process.
Younger students also frequently believe that sound only travels through air and cannot travel through solids or liquids despite their often contradictory experiences of hearing muffled and distorted sounds underwater when swimming.
Older students often still have confused understandings of the difference between the pitch of a sound and how loud it is. Many students believe that these are somehow the same thing or closely connected. They believe that the pitch of a sound will increase as the volume of the sound increases.
Research:
Leite & Afonso (2001),
Hapkiewicz (1992),
Berthelsen (1999),
Boyes & Stanisstreet (1991),
Eshach & Schwartz (2006)
Scientific View
All sounds come from things that vibrate. The faster they vibrate the higher the sound they produce. When things vibrate faster than about 25 vibrations per second we begin to hear a sound of very low pitch. As things vibrate faster the pitch of the sound rises (middle C is 256 vibrations per second, high C is 512.) Even the best human ear can no longer hear sounds when the source of the sound is vibrating faster than about 20,000 vibrations per second. The pitch of a sound is not connected to the volume of the sound. As the human ear ages it becomes less sensitive and its frequency range reduces, particularly in the upper range above 14,000 vibrations per second.
Scientists call the number of vibrations per second the frequency. Vibrations per second are measured in Hertz.
Sound travels through solids, liquids and gases at different speeds. The sound spreads out from the source in the same way as ripples do on water after a stone is thrown into it. As a result of this spreading out the sound striking our ear at a distance is much less intense than it is close to the source. This is why sounds become quieter as we walk away from them and louder as we approach.
The human ear detects vibrations that strike the ear drum and converts these into nerve signals that travel to the brain. The brain uses previous experiences to interpret these as voices, music, noise, etc. Having two ears helps us to better detect where a sound is coming from.
Many animals can detect sound over a much larger frequency range than the human ear. For example, dolphins, bats and dogs can hear vibrations that we cannot.
Critical teaching ideas
- We use our ears to hear a wide range of sounds.
- All sounds come from vibrating objects.
- We can describe different sounds as loud, quiet, high and low and we can use these characteristics of sounds to often identify types of sounds and their sources.
- As we move away from an object making a constant sound, we hear the sound become quieter.
Explore the relationships between ideas about sound in the
Concept Development Maps – Waves
Teaching activities
At this level it is appropriate for students to recognise that hearing is one of their five senses and that hearing involves the use of their ears. Activities should focus on encouraging students to recognise auditory experiences they take for granted. At this level the use of correct scientific language is not considered as important (see the focus idea
Introducing scientific language) as providing practical experiences which help to demonstrate the key ideas.
Provide an open problem to be explored via play or through problem solving
Encourage students to explore a number of different percussion and string instruments to identify which parts of the instruments are responsible for the mechanical movement needed to produce the sound they emit. With guidance students should be able to identify the parts (e.g. the surface of a drum, the strings of a guitar) whose movement or vibration creates the sound waves.
Students could further investigate the sound produced by a vibrating ruler projecting out from the edge of a bench. Have the students strike the end of the ruler and then quickly reduce the overhang on the bench. The rate of vibration will increase, producing a higher pitched sound. Look to focus students’ attention on the mechanical means used to create sound waves.
Provide an open problem to be explored via play or through problem solving
Encourage students to explore their sense of sound with shakers as sound makers. Students should shake a number of things that produce similar sounds. The intended outcome is for students to recognise how well they can distinguish small differences between sounds. Collect some empty 250ml or 374ml plastic bottles with screw tops. Provide a wide range of materials that can be easily placed inside the containers, such as uncooked rice, corn, bean or wheat seeds, sand, sugar, pebbles, glass marbles, ball bearings, coins, rock salt, dried oats, raisins, jelly beans or tooth picks.
Have the students fill the bottles 1/4 to 1/3 full with just one type of item. Seal the top of the bottles with adhesive tape (to avoid having the contents all over the floor) and have the students decorate them to hide the contents. Students can then shake their shakers and compare the sounds made by the different materials.
Have the students play a guessing game with their sound shakers: students guess what is inside the sound shaker just by listening to the noise the shaker makes. A focus for discussion is that our ears are very good at detecting small differences between sounds and we are very good at interpreting what these differences mean. There are lots of other experiences that can be used to illustrate this point – many can be suggested by students.
Another variation is to firstly identify pairs of containers with the same material. Mix up the containers and challenge students to find the missing partner from the similar sound it makes when shaken. Be sure that the same containers are filled with similar quantities of materials to ensure that the sounds they make are similar.
Focus students’ attention on overlooked detail
A surprising number of sound sources can be heard in a classroom when everyone is quiet. Often these background sounds, such as traffic sounds, aircraft noise and building construction sounds go completely unnoticed until identifying them becomes a focus for the students.
Ask the students to identify all the different sounds they can hear. They could write them down or draw a picture of each and make a list. Prompt students by asking, ‘Can you hear a clock, the wind, talking from another classroom, people breathing or coughing, noisy cars, passing aeroplanes, footsteps, emergency vehicles or music?’ Students should try to identify and discuss the sources of the sounds they’re hearing. Try to focus on identifying sounds that are frequently overlooked and encourage the students to describe why the sound was easily identifiable. Were there sounds that the students could hear but not identify?
This activity could be extended with the class doing a ‘sound tour’ around the school grounds. Students could sit and listen for a short time at different points around the school and discuss what they hear.
Open discussion via a shared experience
Create a mystery sound quiz for students. This could be attempted by the whole class with their eyes closed at the same time or several blindfolded individuals seated out the front of the class. Consider creating teams of around 6 students where a member from each is given the same sound to identify. The first team to correctly identify the sound wins points for their team. Create a collection of sound sources which range from easy to identify to very challenging. These could be created on the spot, e.g. ripping newspaper, or recorded as sound bytes to be played back and reused as required. Many sound bytes can be downloaded from the internet.
Sounds could be created by:
- Shaking coins
- Clapping hands
- Tapping a pencil or pen on a desk
- Closing a book
- Crumpling up paper or aluminium foil
- Tearing some cloth or perforated paper
- Closing a stapler or peeling off adhesive tape from a dispenser
- Rolling a glass marble on a desk.
The discussion should guide students to appreciate that their ears are very sensitive and can identify very small differences between similar sounds.
For a variation on the mystery sound quiz, have the students group a range of sounds into sources that are created by a shaking, plucking, banging or blowing different objects. Alternatively group them by the pitch of the sound they make. Is it a high sound or a low sound? Assist the students to draw charts listing each or to physically group similar items. Have them discuss what musical instruments they know work in similar ways. For example, students could identify musical instruments that are all blown, or that all produce low sounds.
Open discussion via shared experience
Blindfold one student and have them sit in the middle of a large class circle. Point to one of the students in the circle and have them make a noise using a whistle or bell. The challenge for the blindfolded student is to try and point in the direction of the sound. Have a number of students try the challenge and then see how much more difficult the task is if the blindfolded student covers one of their ears. After several attempts the added difficulty of using only one ear to locate sound can be discussed.
For a variation on this challenge point to a student around the circle and have them call out the blindfolded student’s name just once. The blindfolded student can then try to locate the direction by pointing and the identity of the student who called their name.
Helping students work out some of the ‘scientific’ explanations for themselves
Encourage students to make a wide range of simple sound producing items using recycled materials. For example, they could design rattles or whistles, stretch rubber bands over empty milk cartons, or design instruments made of pipes of different sizes.
Have the students construct and decorate their items in small groups. Encourage them to investigate how many ways the item can be used to make different sounds. Have them identify the sounds they make when their items are plucked, banged or blown. Students should demonstrate the variety of sounds they can create.
Promote reflection on and clarification of existing ideas
Encourage students to explore and identify loud and soft sounds through practical examples. Ask students to consider how far away they are when they can just hear common sounds such as a person talking, a clock ticking, a chain saw, a cow mooing, a car horn or a bird call. Take students into the school playground and have them investigate how far away they can walk from a constant low level sound (such as a small bell ringing) before they can’t hear it any more.
Explore a number of alternative ways of finding out the distance at which most students can no longer hear the sound. Negotiate with students to decide on the best way of finding this out. Use the method with one source and ask the students to measure how far they were away from the source using steps or plastic cones spaced for the purpose. Repeat using a quieter sound source and record measurements again. Discuss what difference the distance makes to how loud the sound seems to be. Explore whether the students believe the bell is staying the same (i.e. making a constant ringing sound) or ringing more quietly when they move away from it.
Further resources
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Hearing: Audition – this Neuroscience of Kids site provides further activities and was used to design some of the activities above.
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Physics: Sound for Elementary – this Science Museum of Minnesota site provides more ideas for classroom activities.
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Making Sense of Sound – this Exploratorium site provides online listening activities for students.