5.5 and 5.6 Pitch and Frequency,, calculations sound

• Science
• Middelbare school
• vwo
• Leerjaar 1

Recap

Four wave properties:

1. Wave length

2. Amplitude

3. Frequency 

4. Speed

v=f⋅λ

You saw the frequency increasing. What happened to the pitch if the frequency increases? As the f increases pitch increases too.

       A. What was the highest frequency you heard?

Somwhere between 20 to 23000 Hz.

      

For this exercise use the table at the previous page. You only need two names.

Animal which can hear the highest frequency

Animal that hears the lowest frequency

Neither of the two choices

Elephant

Porpoise

Bats

Dog

Cat

Chicken

Killer Whale

What frequency can be heard by all animals?

1. 16 Hz
2. 2.000 Hz
3. 150.000 Hz
4. None of the one mentioned

Two formulas to calculate the speed of sound

speed=​time​​distance​​

speedofsound=wavelength⋅frequency

speed=​time​​distance​​

v=​t​​d​​

• v: speed in m/s
  
• d: distance in m
  
• t: time in s
  

3=​2​​6​​

• v_s: the speed of sound (m/s)
  
• λ: wavelength (m)
• f: frequency (Hz)
  

speedofsound=wavelength⋅frequency

v_s = λ • f

6=2⋅3

Formula frequency 

f = 1/T  where,

f: frequency in hertz (Hz)

T: time needed for one vibration in seconds

T=1/f

Definition supersonic and Mach

Supersonic: faster than speed of sound

Mach 1 = speed of sound in air = 330 m/s

Mach 3 = 330× 3= 990 m/s

Opgave 

 a sound wave were observed to travel a distance of 700 meters in 2 seconds. Calculate its speed.

Given: d= 700 meter , t= 2 s

Asked: v=?

v=d/t.  v= 700/ 2= 350 m/s

Opgave

What is the speed of a sound wave with a frequency of 2 kHz and a wavelength of 35 cm? 

Given: f= 2kHz. = 2000 Hz.    

λ= 35 cm = 0.35 m

Asked: v=?  

v = λ • f = 0.35× 2000= 700 m/s

Calculating the speed of sound  using echoes

A girl stands 102 m away from a wall and claps two wooden blocks together. She hears an echo after 0.6 s.Calculate the speed of sound in air. 

Given: t = 0.6 s.  d=102 + 102 = 204 m.

Asked: v=?

v=d/t  = 204÷ 0.6=340 m/s 

Or  v=d/t. v= 102÷ 0.30 = 340 m/s