Topicmf38a83426dbba978_1528449000663_0Topic

Infrasound

Levelmf38a83426dbba978_1528449084556_0Level

Second

Core curriculummf38a83426dbba978_1528449076687_0Core curriculum

VIII. Vibrating motion and waves. The student:

8) distinguishes audibleaudibleaudible sounds, ultrasounds and infrasound; lists examples of their sources and applications.

Timingmf38a83426dbba978_1528449068082_0Timing

45 minutes

General learning objectivesmf38a83426dbba978_1528449523725_0General learning objectives

Presentation of the properties of infrasound.

Key competencesmf38a83426dbba978_1528449552113_0Key competences

1. Definition of infrasoundinfrasoundinfrasound.

2. Presentation of properties and parameters of infrasound.

Operational (detailed) goalsmf38a83426dbba978_1528450430307_0Operational (detailed) goals

The student:

- can define infrasound and indicate their properties,

- presents natural and artificial sources of infrasound.

Methodsmf38a83426dbba978_1528449534267_0Methods

1. Discussion about new material.

2. Discussion developing in the course of common problem solving by a class or group.

Forms of workmf38a83426dbba978_1528449514617_0Forms of work

1. Group work.

2. Cooperation with the teacher while solving problems.

Lesson stages

Introductionmf38a83426dbba978_1528450127855_0Introduction

Prepare answers to the following questions:

1. What is a sound wave?
2. List the features of the sound.
3. What is the range of audible frequencies?

Proceduremf38a83426dbba978_1528446435040_0Procedure

What is infrasoundinfrasoundinfrasound?

Infrasound is the vibrations of the medium in which they diverge at frequencies below the audible frequencyfrequencyfrequency.

The infrasonic range is taken as a band with frequencies between 0,1 and 20 Hz. Infrasound wave length is above 17 m, therefore weakly attenuated waves can propagate over long distances.

Can you hear infrasound?

Infrasound that is part of the noise is not audible. But it is picked up by the body, in a specific way, through the auditory path (mainly through hearing organs). The audibility of these infrasound is dependent on the sound pressure level.

Some animals, such as elephants and whales, can communicate with each other using infrasound.

Indicate the natural sources of infrasound.

The natural sources of infrasoundinfrasoundinfrasound are:

- earthquake,
- eruption of volcanoes,
- auroras,
- ocean waves,
- hurricane wind,
- sinking of masses of water from large waterfalls.

Find artificial sources of infrasound.

Artificial sources of infrasound generated by man.

Infrasound can be encountered in large office buildings industrial buildings.

The source of this infrasound are machines and devices. Ventilation and air conditioning ducts strengthen these sounds.

InfrasoundinfrasoundInfrasound is generated by:

- vibratiges, ons of brid,
- operation of wind farms,
- work of jet engines,
- explosions.

[Slideshow]

Introduce the properties of infrasound.

Properties of infrasound:
- They spread very well in the air and over long distances. There is practically no change in the intensity of infrasound.
- Infrasound disperses at the speed of sound waves.
- Infrasound is not suppressed by acoustic screens or their attenuation is very small.
- People cannot hear infrasound, but they can feel it. Infrasound effects on the human body are very unpleasant, infrasound is dangerous at high volumes.
- Infrasound can cause feelings of anxiety and fear. The effect of infrasound is nausea and headaches. They disrupt the sense of balance. Due to the lack of advisability to build shields to protect against infrasound, they arouse interest in military use. Of course, these tests are classified.
- Some animals can hear infrasound and they use it to communicate at very long distances. Among them there are giraffes, elephants and whales.
mf38a83426dbba978_1527752256679_0Properties of infrasound:
- They spread very well in the air and over long distances. There is practically no change in the intensity of infrasound.
- Infrasound disperses at the speed of sound waves.
- Infrasound is not suppressed by acoustic screens or their attenuation is very small.
- People cannot hear infrasound, but they can feel it. Infrasound effects on the human body are very unpleasant, infrasound is dangerous at high volumes.
- Infrasound can cause feelings of anxiety and fear. The effect of infrasound is nausea and headaches. They disrupt the sense of balance. Due to the lack of advisability to build shields to protect against infrasound, they arouse interest in military use. Of course, these tests are classified.
- Some animals can hear infrasound and they use it to communicate at very long distances. Among them there are giraffes, elephants and whales.

Lesson summarymf38a83426dbba978_1528450119332_0Lesson summary

Infrasound - these are acoustic waves (sounds) with frequencies frequencies between 0,1 and 20 Hz. They are inaudible to human beings. In natural conditions they arise, during explosions, lightning, earthquakes and, for example, waves of water. At an appropriate high sound pressure level, they have a negative effect on humans. They cause concern and nausea, and even states of depression, etc. Infrasound is picked up not only by the ears but also by vibration receptors, for example on the skin or in tendons, muscles and joints. These sounds at such a low frequency may cause resonance vibrations, in particular, in the chest, throat or abdominal cavity.mf38a83426dbba978_1527752263647_0Infrasound - these are acoustic waves (sounds) with frequencies frequencies between 0,1 and 20 Hz. They are inaudible to human beings. In natural conditions they arise, during explosions, lightning, earthquakes and, for example, waves of water. At an appropriate high sound pressure level, they have a negative effect on humans. They cause concern and nausea, and even states of depression, etc. Infrasound is picked up not only by the ears but also by vibration receptors, for example on the skin or in tendons, muscles and joints. These sounds at such a low frequency may cause resonance vibrations, in particular, in the chest, throat or abdominal cavity.

Selected words and expressions used in the lesson plan

acoustic screensacoustic screensacoustic screens

audibleaudibleaudible

frequencyfrequencyfrequency

infrasoundinfrasoundinfrasound

pressurepressurepressure

resonanceresonanceresonance

sound propagationsound propagationsound propagation

soundssoundssounds

vibrationsvibrationsvibrations

wavelengthwavelengthwavelength

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audible1
audible

słyszalny

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infrasound1
infrasound

infradźwięki

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frequency1
frequency

częstotliwość

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sounds1
sounds

dźwięki

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sound propagation1
sound propagation

propagacja dźwięków

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vibrations1
vibrations

wibracje

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acoustic screens1
acoustic screens

ekrany akustyczne

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wavelength1
wavelength

długość fali

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resonance1
resonance

rezonans

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pressure1
pressure

ciśnienie

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