3B Scientific Acoustics Kit User Manual
3B SCIENTIFIC
Instruction sheet
05/09 ELWE/ALF
®
PHYSICS
Acoustics Kit U8440012
1. Description
This set of apparatus makes it possible to impart an
extensive and well-rounded overview on the topic
of acoustics. The set can be used for conducting
numerous experiments.
Sample experiments:
1. String tones
2. Pure acoustic tones
3. Vibrating air columns
4. Open air column
5. Whistle
6. Vibrating rods
7. Infrasound
8. Ultrasound
9. Tuning fork with plotter pen
10. Progressive waves
11. Doppler effect
12. Chladni figures
13. Chimes
14. Standing waves
15. Overtones
16. Measurement of wavelength
17. Soundboard
18. Resonator box
19. Spherical cavity resonator
20. Stringed instruments and the laws they obey
21. Scales on stringed instruments
22. Measurement of string tension
23. Relation between pitch and string tension
24. Wind instruments and the laws they obey
25. C major scale and its intervals
26. Harmony and dissonance
27. G major triad
28. Four-part G major chord
29. Major scales in an arbitrary key
30. Introduction of semitones
The set is supplied in a plastic tray with a foam
insert that facilitates safe storage of the individual
components.
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2. Contents
1 Trays with foam inserts for acoustics kit
2 Monochord
3 Bridge for monochord
4 Metallophone
5 Chladni plate
6 Tuning fork, 1700 Hz
7 Tuning fork, 440 Hz
8 Tuning fork with plotter pen, 21 Hz
9 Spring balance
10 Retaining clip
11 Table clamp
12 Helmholtz resonators
70 mm dia.
52 mm dia.v
40 mm dia.
34 mm dia.
13 Glass tube for open air column
14 Kundt’s tube
15 Glass tube for closed air column
16 Rod for Chladni plate/bell dome
17 Galton whistle
18 Plotter pen with holder
19 Lycopodium powder
20 Plastic block for clamp
21 Rubber top
22 Bell dome
23 Reed pipe
24 Whistle
25 Steel string
26 Nylon string
27 Resonance rope
28 Plunger
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3. Technical data
Dimensions: 530 x 375 x 155 mm3 approx.
Weight: 4.5 kg approx.
4. Sample experiments
1. String tones
• Pluck the monochord string hard when it is
moderately taut.
• Subsequently increase the tension on the string
by turning the peg to the right. Pluck the string
again.
At first, a low tone is heard. As the string is tightened the tone gets higher.
Reasons: vibrating strings generate acoustic tones
by inducing alternating compression and rarefaction of the surrounding air. The greater the tension
in the string, the faster the vibrations are and the
higher the tone.
2. Pure acoustic tones
• Hit the 440 Hz tuning fork hard with the metal-
lophone beater.
A pure acoustic tone of a very specific, unchanging
pitch can be heard. This tone dies away very slowly.
Reasons: a tuning fork consists of a U-shaped steel
piece which merges into the stem at its vertex. As
the tuning fork only vibrates in one oscillation
mode (with both prongs either both moving apart
or both moving towards one another), it produces a
pure tone of an unchanging pitch. Owing to its
property of producing a constant pitch, tuning
forks are used for tuning musical instruments.
3. Vibrating air columns
• Attach the glass tube for demonstrating a
closed air column by means of the table clamp,
plastic block and retaining clip.
• Insert the tuning plunger into the glass tube.
• Hit the 440 Hz tuning fork hard with the metal-
lophone beater. By pulling out the plunger to a
greater or lesser degree it is possible to alter
the length of the closed air column.
There is only one plunger position at which the air
column resonates strongly. At any other position
there is no sound. Resonance can be detected by
the increase in sound volume.
Reasons: a closed air column starts resonating
when its length corresponds to one quarter of the
excitation wavelength. The tuning fork vibrates
with a frequency of 440 vibrations per second.
Applying the following equation:
Wavekength =
⋅
⋅
scm
/34000
pagationSpeedofpro
Frequency
sfreqExciting
/440
cm
⋅=
2.77
the wavelength of the tone produced is 77.2 cm.
One quarter of this wavelength is therefore
19.3 cm.
The distance between the plunger and the opening
at the end of the tube is 19.3 cm when resonance
occurs.
4. Open air column
• Conduct the same experiment with an open air
column (14).
The open air column, which is exactly double the
length of the closed air column, starts resonating
when the tuning fork is brought into its vicinity, as
can be heard by means of the increased volume.
Reasons: an open air column starts resonating
when its length is half that of the wavelength or
multiples of that length. Antinodes are formed at
the ends of the open air column and a node at the
middle.
5. Whistle
• Blow the whistle and change its length by
gradually drawing out the plunger.
Depending on the length of the whistle, its note
gets higher or lower but the character or timbre of
the note remains the same.
Reasons: blowing a uniform air stream into the
opening of a whistle causes the air trapped in the
pipe to vibrate and eddies then occur at regular
intervals air the air passes over the blade. The
resulting tone depends on the length of the air
column. In the case of a closed air column, the
length of the whistle (measured from the edge of
the blade to the base of the whistle) corresponds to
a quarter wavelength of the base tone. A node is
formed at the blade of the whistle and an antinode
is formed at the end of the pipe
6. Vibrating bars
• Use the striking hammer supplied to strike
several bars of the metallophone. When the
metal bars are struck, they produce a distinct,
melodious note, each of which has a similar
timbre. The shorter the length of the bar, the
higher the tone.
Reasons: elastic rods form systems capable of oscillating if they are resting upon a point where a node
is formed (about 22% of the total length between
the two ends).
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