Calculate with sound
Calculate with sound
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Slide 1: Slide
physicsMiddelbare schoolhavo, vwoLeerjaar 2
This lesson contains 28 slides, with text slides.
Lesson duration is: 45 minItems in this lesson
Calculate with sound
Slide 1 - Slide
Formulas:
f = 1/T
T = period in s
f = frequency in Hz
T = 1/f
f = frequency in Hz
T = period in s
Converting
ms to s (: 1000)
kHz to Hz (x 1000)
Hz to kHz (:1000)
s = v x t
v = speed in m/s
t = time in s
s = distance in m
G.A.S.
Given
Asked
Solution
Slide 2 - Slide
1. Calculate
time/div = 0.2 ms/div
Calculate the frequency
Slide 3 - Slide
2. Tones
a. Which picture shows the highest tone?
b. Which picture shows the lowest tone?
c. Which picture shows the loudest tone?
Slide 4 - Slide
3.
You see a musical box. When you rotate the handle, you hear a melody.
a. Which bars produce the lowest tones, the short or the long ones?
b. Which bars produce the highest tones?
Slide 5 - Slide
4. Oscilloscope
a. Read the period of one vibration (click on picture to enlarge).
b. Calculate the frequency.
Slide 6 - Slide
5. Piano
A piano string produces vibrations with a period of 2.5 ms.
a. Convert the period into seconds.
b. What is the frequency f?
c. Convert the frequency to kHz.
Slide 7 - Slide
6. Air-raid siren
This is an old fashioned air-raid siren. Air is driven via a tube onto the rotating disc. The air is forced through 30 holes in the disc. This creates a vibration which produces a loud sound. The disc rotates 5 times per second.
Slide 8 - Slide
6.
a. How many times per second does a hole appear below the opening of the air pipe?
b. Explain why you hear a tone of 150 Hz
Slide 9 - Slide
6
The siren starts slowly and the gradually becomes higher. At full speed the tone is 1.8 kHz.
c. Calculate the periode of this frequency.
d. How many times per second does the disc rotate now?
Slide 10 - Slide
7
At a firework display, Phil sees a rocket explode 124 m above his head. The sound of speed is 340 m/s.
Calculate how much later Phil hears the bang.
Slide 11 - Slide
1. Calculate
time/div = 0.2 ms/div
Calculate the frequency
Slide 12 - Slide
1.
Given: 0.2 ms/div
1 vibration is 5 blocks (div)
Asked: f
Solution: f = 1/T
T = 5 x 0.2 ms = 1 ms
1 ms :1000 = 0.001 s
f = 1 / 0.001 s = 1000 Hz
Slide 13 - Slide
2. Tones
a. Which picture shows the highest tone?
b. Which picture shows the lowest tone?
c. Which picture shows the loudest tone?
Slide 14 - Slide
2.
a. C- most vibrations in 0.01 s
b. B- least amount of vibrations in 0.01 s
c. A - biggest displacement (in y-direction)
Slide 15 - Slide
3.
You see a musical box. When you rotate the handle, you hear a melody.
a. Which bars produce the lowest tones, the short or the long ones?
b. Which bars produce the highest tones?
Slide 16 - Slide
3.
a. The longest ones
b. The shortest ones
Slide 17 - Slide
4. Oscilloscope
a. Read the period of one vibration (click on picture to enlarge).
b. Calculate the frequency.
Slide 18 - Slide
4.
a. One vibration lasts 1.82 ms (easiest to see from 6 to 7.82 ms)
b. Given: T = 1.82 ms = 1.82:1000 = 0.00182 s
Asked: f
Solution: f = 1/T
f = 1 / 0.00182 = 549,5 Hz
Slide 19 - Slide
5. Piano
A piano string produces vibrations with a period of 2.5 ms.
a. Convert the period into seconds.
b. What is the frequency f?
c. Convert the frequency to kHz.
Slide 20 - Slide
5.
a. T= 2.5 ms = 2.5 : 1000 = 0.0025 s
b. Given: T = 0.0025 s
Asked: f
Solution: f = 1/T
f = 1/ 0.0025 = 400 Hz
c. f = 400 Hz = 400 : 1000 = 0.4 kHz
Slide 21 - Slide
6. Air-raid siren
This is an old fashioned air-raid siren. Air is driven via a tube onto the rotating disc. The air is forced through 30 holes in the disc. This creates a vibration which produces a loud sound. The disc rotates 5 times per second.
Slide 22 - Slide
6.
a. How many times per second does a hole appear below the opening of the air pipe?
b. Explain why you hear a tone of 150 Hz
Slide 23 - Slide
6
The siren starts slowly and the gradually becomes higher. At full speed the tone is 1.8 kHz.
c. Calculate the period of this frequency.
d. How many times per second does the disc rotate now?
Slide 24 - Slide
6
a. The disc turns 5 times per second. 5 Times the 30 holes in the disc are 150 holes. 150 Holes pass the air pipe per second.
b. Every time the air is blown into the hole and then interrupted by the solid part in between the holes, creates a sound. This happens 150 times per second = at a frequency of 150 Hertz.
Slide 25 - Slide
6
c. f = 1.8 kHz = 1.8 kHz x 1000 = 1800 Hz
T = 1/f = 1/1800 = 0.00056 sec
d. Given f = 1800 Hz
30 holes in the disc
Asked: amount of rotations per second
Solution: 1800 holes pas per second
1800 : 30 holes per rotation = 60 rotations per second
Slide 26 - Slide
7
At a firework display, Phil sees a rocket explode 124 m above his head. The sound of speed is 340 m/s.
Calculate how much later Phil hears the bang.
Slide 27 - Slide
7
Given: s (distance) = 124 m
v (speed) = 340 m/s
Asked: t (time)
Solution: s = v x t
t = s / v = 124 m / 340 m/s = 0.36 seconds
Phil hears the blast after 0.36 seconds.
