Topicmf74bbb76ce807d52_1528449000663_0Topic

Loud or quiet - sound intensity

Levelmf74bbb76ce807d52_1528449084556_0Level

Second

Core curriculummf74bbb76ce807d52_1528449076687_0Core curriculum

VIII. Vibrating motion and waves. The student:

7) describes qualitatively the relationship between sound pitch and wave frequency and the relationship between the volume of the sound (loudness) and wave energy as well wave amplitude.

Timingmf74bbb76ce807d52_1528449068082_0Timing

45 minutes

General learning objectivesmf74bbb76ce807d52_1528449523725_0General learning objectives

Introducing the concepts of sound intensity and the level of sound intensity.

Key competencesmf74bbb76ce807d52_1528449552113_0Key competences

1. Defining the concept of sound powersound powersound power.

2. Introducing of the concept of sound intensitysound intensitysound intensity.

3. Presenting the concept of the level of sound intensitylevel of sound intensitylevel of sound intensity.

Operational (detailed) goalsmf74bbb76ce807d52_1528450430307_0Operational (detailed) goals

The student:

- uses the concept of sound intensity,

- uses the concept of the level of sound intensity to solve problems.

Methodsmf74bbb76ce807d52_1528449534267_0Methods

1. Problem lecture.

2. Formulating problems and ideas for solving them.

Forms of workmf74bbb76ce807d52_1528449514617_0Forms of work

1. Work in groups.

2. Making notes during the lesson.

Lesson stages

Introductionmf74bbb76ce807d52_1528450127855_0Introduction

Answer the introductory questions:

1. What is the sound wave?

2. List the properties of the sound wave.

3. Does the propagating sound wave transfer energy?

4. Is every sound every the range 16 Hz to 20 kHz audible to us?

Proceduremf74bbb76ce807d52_1528446435040_0Procedure

The ear collects energy only from the area which it occupies. For the sensation of volume, the energy expressed in a unit of time per a unit of surface is important.

A volume of the sound is its characteristic property. The volume represents the ratio of energy transmitted by the sound wave in a time unit per surface. Thus, it is the ratio of the sound powersound powersound power in relation to a particular surface.

where:
$E$ - volume of sound in relation to the surface $S$,
$P_{\mathrm{acoustic}}$ - the power of the acoustic wave reaching the surface $S$ (the power emitted by the sound source in the form of an acoustic wave),
$S$ - the surface which the sound falls on.

A 10 times higher volume is not perceived by a human as 10 times louder sound.

That is why we enter a unit called the sound level [dB]. To determine the level of sound intensity, the reference frequency is set to f = 1000 Hz. For her, the threshold of hearing is $E_0={10}^{-12}\frac{W}{m^2}$. This is the zero point of the new scale. The intensity of 10 times greater is 10 dB, 100 more is 20 dB etc.

[Illustration 1]

Area of hearing:
In order to hear a given sound, it is not enough that the frequency of sound is in the range of 116 Hz – 20000 Hz (20 kHz). The volume of sound should also be over a certain threshold, below which we will not perceive auditory sensations. It is called „the hearing threshold”.

However, above a certain volume of sound, it is not possible to perceive any auditory sensations. We will only feel pain. In his case the threshold of the volume of sound is called „the pain threshold”.

[Illustration 2]

[Illustration interactive]

Sample values of sound level:

10 dB - rustling of leaves with a moderate wind,
20 dB - whisper,
30 dB - very quiet street without traffic,
40 dB - rustle at home,
50 dB - rustle in offices,
60 dB - vacuum cleaner,
70 dB - the interior of a noisy restaurant, tearing paper, the interior of a car,
80 dB - loud music indoors, toot,
90 dB - traffic,
100 dB - motorcycle without a silencer,
110 dB - chainsaw,
120 dB - helicopter rotor at a distance of 5 meters,
140 dB - start of a jet fighter,
160 dB - explosion of firecrackers,
190 dB - launch of a spacecraft,
220 dB - atomic bomb explosion.mf74bbb76ce807d52_1527752263647_010 dB - rustling of leaves with a moderate wind,
20 dB - whisper,
30 dB - very quiet street without traffic,
40 dB - rustle at home,
50 dB - rustle in offices,
60 dB - vacuum cleaner,
70 dB - the interior of a noisy restaurant, tearing paper, the interior of a car,
80 dB - loud music indoors, toot,
90 dB - traffic,
100 dB - motorcycle without a silencer,
110 dB - chainsaw,
120 dB - helicopter rotor at a distance of 5 meters,
140 dB - start of a jet fighter,
160 dB - explosion of firecrackers,
190 dB - launch of a spacecraft,
220 dB - atomic bomb explosion.

[Illustration 3]

Lesson summarymf74bbb76ce807d52_1528450119332_0Lesson summary

The volume of the sound is a quantity which describes the power of the acoustic wave per a unit area $\left[\frac{W}{m^2}\right]$. A unit called the sound level [dB] is introduced. f = 1000 Hz is the reference value of frequency. Thus, the hearing thresholdhearing thresholdhearing threshold equals $E_0={10}^{-12}\frac{W}{m^2}$. This is the zero point of the new scale.

In order to hear a given sound, it is not enough that the frequency of sound is in the range of 16 Hz - 20 kHz. The volume of sound should also be over a certain threshold, below which we will not perceive auditory sensationsauditory sensationsauditory sensations. It is called „the hearing threshold”.

However, above a certain volume of sound, it is not possible to perceive any auditory sensationsauditory sensationsauditory sensations. We will only feel pain. In his case the threshold of the volume of sound is called „the pain thresholdpain thresholdpain threshold”.

Selected words and expressions used in the lesson plan

auditory sensationsauditory sensationsauditory sensations

deafnessdeafnessdeafness

hearing thresholdhearing thresholdhearing threshold

level of sound intensitylevel of sound intensitylevel of sound intensity

measurementmeasurementmeasurement

noisenoisenoise

pain thresholdpain thresholdpain threshold

sound intensitysound intensitysound intensity

sound powersound powersound power

sound sourcesound sourcesound source