Category Archives: Acoustics

Range of Hearing

Demo: OW-C-RH
Pira Index: 3C 20.10

 Lab Equipment  Directions
  1.  Pasco function generator
  2. Pasco speaker
  1.  Plug the speaker into the function generator as shown. The function generator should be set to sine wave shape and the amplitude about half way up.
  2. Start the frequency at ~20 Hz or below and ask students to raise their hand when they hear a sound.
  3. Slowly increase frequency asking students to put their hand down when they no longer hear a tone. Some will hear up to ~20,000 Hz.


Fourier Synthesis – Pasco

Demo: OW-C-FS
Pira Index: 3C 50.10

 Lab Equipment  Directions
  1.  Pasco #9307 Fourier synthesizer
  2. Philips PM 3055 oscilloscope
  3. speaker (Auratone) with phono-DB adaptor
  4. 2 BNC to DB leads
  5. BNC-f to DB-m adaptor
  1.  Connect both leads, watching polarity on the DB connectors.
  2. Turn on power and slide 1st IN/OUT switch to ‘IN.’ Use autoset button on scope to obtain sine wave.
  3. Slide 2nd column #1 switch to ‘IN’, then columns 3, 5, and 7 to ‘IN’ to mix in other harmonics.
  4. Follow settings description for triangle wave. For square waves slide 1st column to 90 degree and make minor amplitude adjustments on 1, 3, 5, and 7.


Acoustic Disk

Demo: OW-C-AD
Pira Index: 3C 20.30

 Lab Equipment  Directions
  1.  acoustic disk
  2. air jet attachment with hose
  3. variable speed rotator
  4. air/vacuum pump
  1.  Insert the acoustic disk in the collet of the variable speed rotator. (may be already done)
  2. Attach the air jet to the air pump and hold the jet over the disk when it spins.
  3. Turn on the rotator (adjust the speed if needed) varying tones are emitted by each row of holes. The rows are respectively, 24, 24, 30, 36, and 48 holes.