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Siemens Stiftung

Sound diffraction

Graphic:
Diffraction is a typical feature of sound waves when they meet an obstacle.

The diffraction of sound waves is a physical mechanism which ensures the entry of sound waves into acoustic shadows.
That means the sound is audible in areas which are cut off from the direct sound incidence, such as behind obstacles.

Information and ideas:
Diffraction of light can be proved when a parallel ray beam of monochrome light is directed at a narrow opening. A screen set up behind the opening gives us a diffraction figure (bright and dark stripes that lose intensity the further outwards they are). With sound, a direct reference to the students' everyday world is even easier: Why can you hear noise from a street in front of a building even when you are behind the building?
Further information about this graphic is provided as an information sheet on the media portal of the Siemens Stiftung.

Relevant for teaching:
Sound/acoustics: parameters
Vibrations and waves

Medientypen

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Lernalter

13-18

Schlüsselwörter

Chart Optics Sound Wave (physics)

Sprachen

Englisch

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Siemens Stiftung

Sound refraction

Schematic diagram:
Sound refraction in air with different temperature layers (from warm to cold).

The speed of sound in the air depends on the density and thus the temperature of the air: At high temperatures, the sound travels faster than it does at lower ones. So when sound moves from a warm layer of air to a colder one, its speed decreases.
However, the direction in which the sound spreads also changes as the speed changes. It is said that the sound wave is "broken?. In the case described, i.e. when sound moves from a warm to a cold layer of air, the sound wave is broken upwards.

Information and ideas:
How does sound behave when it moves from a colder to a warmer layer?
Is it correct that you hear worse against the wind than with the wind?
The latter can be checked together with students in an experiment.
A comparison with the refraction of light rays can be made.

Relevant for teaching:
Sound/acoustics: parameters
Vibrations and waves

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Siemens Stiftung

The Ear, Hearing and Hearing Impairment;: Vibrations and waves

Overview graphic:
Overview of the most important parameters of vibrations and waves.

Electromagnetic waves are vibrations in the electrical and magnetic field that propagate through space at the speed of light. The parameters of vibrations and waves, such as frequency, are presented in an overview.

Instructions and ideas:
As overview information for students on the topic of "vibrations and waves". Important basis for understanding sound waves in acoustics.

Medientypen

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Lernalter

11-18

Schlüsselwörter

Chart Optics Sound Wave (physics)

Sprachen

Englisch

Dieses Material ist Teil einer Sammlung

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Siemens Stiftung

Sound field and sound absorption

Schematic diagram:
Concentric propagation of sound waves. The lines of the same loudness are shown which decreases as the distance to the sound source increases.

Why do we hear less the further away we are from the source of sound?
Sound propagates from its source in a circular way, the sound energy spreads over an increasingly large area and the sound pressure decreases accordingly.
In a free sound field it decreases by about 6 dB every time the distance to source is doubled. Within a room, however, this only applies very close to the sound source.

Information and ideas:
Useful for discussing why we hear less the further away the sound source is.

Relevant for teaching:
Sound/acoustics: parameters
Vibrations and waves
Communication and understanding

Medientypen

Bild

Lernalter

11-18

Schlüsselwörter

Chart Sound Wave (physics)

Sprachen

Englisch

Dieses Material ist Teil einer Sammlung

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Siemens Stiftung

Perforation of the eardrum

Labeled graphic:
Simplified illustration of a perforated eardrum.

A perforated eardrum can occur when foreign bodies, for example, instruments to clean the ears, are stuck in too far or when there are loud bangs near the ear.
Violent blows to the ear can also cause perforation.

Minor tears or perforations can heal up by themselves provided they get the proper treatment. In any case, a doctor should always be consulted!

Information and ideas:
Can be used for illustration purposes on the subject of "Ear diseases" either on transparencies or worksheets. Supposedly "harmless" minor problems can turn into serious damage to the ear.

Relevant for teaching:
Hearing defect/hearing impairment

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Siemens Stiftung

Phase diagram of water

Diagram:
A P-T diagram for pure water. The lines indicate the temperature and the pressure at which the solid, liquid, and vapor phases exist in equilibrium. All three phases exist in equilibrium only at the triple point; otherwise, there are a maximum of two phases.

In addition to the equilibrium curves (melting pressure curve, sublimation curve, vapor pressure curve), the diagram also includes the pressure and temperature data for the melting, boiling, triple, and critical points.
Attention: The axes of the diagram are not shown true to scale.

Information and ideas:
This diagram also reflects the density anomaly of water (lower density in the solid state than in the liquid state): The melting pressure curve shows a negative slope. The reason for the density anomaly is the hydrogen bonds.

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Siemens Stiftung

Speech signal - individual word

Chart:
Screenshot of the oscillographic curve of the spoken word "dogs".

Speech sounds are fluctuating sound signals where the composition of frequencies changes all the time.
Aperiodical overlap periodical parts. Unlike noises, some of which have similar frequency curves, sound in speech is always the carrier of meaning or of messages sent out by the speaker. Other noises like smacking of lips, hissing, rhythms, basic pitch are typical of the individual (acoustic fingerprint) but not essential for the speech content!

Information and ideas:
Supplementary to worksheets and transparencies.

Relevant for teaching:
Sound/acoustics: parameters
Vibrations and waves
Communication and understanding

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Siemens Stiftung

Speech recognition sentence - syllable - phoneme

Chart:
The components of speech, from phoneme to sentence presented visually.

The graphic shows the oscilloscope curve of the spoken sentence "It?s raining cats and dogs" and excerpts from the units from which speech is composed: sentence, word, phoneme.

Information and ideas:
Speech recognition and speech synthesis are very topical themes in the field of information and communication technology.
Further information on this graphic is available as information sheet on the media portal of the Siemens Stiftung.

Relevant for teaching:
The human body
Structure and function of a sense organ
Reception of impulses and information transmission
Sensory perception

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Siemens Stiftung

How long will our energy sources last?

Chart:
A bar chart shows an overview of the remaining years of use of primary energy sources.

Of the fossil energy sources, petroleum will be the first to run out. What is the situation for the other fossil energy sources? Can new technologies delay the point in time when they run out? And is it really true that renewable energy sources never run out?
The time axis has a logarithmic scale.

Information and ideas:
Students learn that the logarithmic scale represents numbers ranging over several powers. More in-depth information regarding how long energy sources will last is provided in the "An overview of energy sources? information sheet.


Dieses Material ist Teil einer Sammlung

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Siemens Stiftung

The Ear, Hearing and Hearing Impairment: Sound absorption

Graphic:
If sound waves strike an obstacle with a corresponding material structure, they are absorbed, i.e. the entire mechanical energy of the sound is converted into thermal energy.

This effect is enhanced by sound barrier walls made of porous materials. By means of multireflection and dispersion, the passage of sound in such materials is extended considerably. The sound peters out.

Information and ideas:
Reference to students' everyday world: silence after snowfall.
Can be checked with the students in an experiment.

Relevant for teaching:
Sound/acoustics: parameters
Vibrations and waves