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Sound Waves and Pressure

Investigation 1 – PreLab









Sound makes up most of our lives. We use it for safety reasons; like when we step out of a street because of an oncoming car. We use it for enjoyment; like when we listen to music or watch TV. And we use it for communication; like when we tell each other about exciting scientific discoveries!


Audiologists are ear specialists. Typically, these professionals work with patients who have problems with hearing, balance, or other ear-related problems.


This Investigation is designed to help you to answer the following Focus Question:

  • How are sounds produced? 
  • How is sound transferred from one object or substance to another? 
  • What is the relationship between the wavelength and frequency of a standing wave and the sound it produces? 

Note: These questions are located in your SDR at the beginning and end of the Investigation.



As a class, read the Background(s) in the Investigation. When finished, discuss the following concepts as a class:

  • Sounds are generated when any solid, liquid or gas vibrates.
  • Vibrations occur when the particles or molecules of matter move repeatedly back and forth. This back and forth movement can be fast or slow depending on the type of matter and the object that is vibrating.
  • Vibrations in one object can cause other, neighboring objects to vibrate.
  • Since sounds are caused by vibrations, the sounds made by the vibrations can also be transferred from one vibrating object to another.
  • Vibrations that cause sound to travel from one object to another in waves are called pressure waves.
  • Pressure waves can occur in all types of matter.
  • If vibrations occur rapidly, they occur frequently and with a high frequency.
  • If vibrations occur slowly, they occur infrequently and with a low frequency.
  • The back and forth motion of vibrating matter takes the form of a standing wave.
  • The two endpoints of the standing wave are called nodes and the middle point is called an antinode.
  • As the vibrations in a standing wave alternate back and forth, pressure is alternately placed on the surrounding air, producing a pressure wave that produces sound.
  • The length of the complete standing wave and is called the wavelength.
  • The frequency and the wavelength have an inverse relationship. This means that if the frequency is low, then the wavelength is long. If the frequency high, then the wavelength is short.




The following list includes Key Terms that are introduced in the Investigation Background(s). They should be used, as appropriate, by teachers and students during everyday classroom discourse.

  • vibration
  • standing wave
  • node
  • antinode
  • pressure wave
  • frequency
  • wavelength
  • pitch

Note: Definitions to these terms can be found on the Introduction page to the CELL.

Note: Additional words may be bolded within the Background(s). These words are not Key Terms and are strictly emphasized for exposure at this time.


  • Complete the Prediction section in your SDR. 
    • What is sound?
    • How can sounds be different from one another?
    • How do we detect sounds?
  • All matter is able to vibrate and that these vibrations are what cause sound.
  • Place your forefinger and thumb on either side of the front of your throat and hum.
  • What do you hear and feel. You should be able to feel your vocal cords vibrating and hear the humming. The back and forth vibrations of your vocal cords cause the sound that you hear.
  • The vibrations of your vocal cords cause the surrounding air to vibrate and the vibrations of the gas molecules in the air cause your eardrums to vibrate. This allows you to hear the sound of your humming or of any other sound
  • Play the video below. Remember to follow along with your SDR and make any notes that you think might be helpful in the lab.
  • After the video, divide into your lab group to discuss strategy for the lab. For example, you may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow you to anticipate the laboratory experience you will soon encounter. You should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.

Note: Homework is posted below the video.


You should review the Investigation and video in preparation for the Lab.