Lesson: How Does a Sound Sensor Work?

Contributed by: GK-12 Program, Computational Neurobiology Center, College of Engineering, University of Missouri

Three images: (left) A small wheeled robot made of plastic parts, cables and buttons with a small box-shaped sound sensor attached to it. (middle) A cutaway drawing shows the human ear anatomy including the external auditory canal, tympanic membrane, malleus, incus, stapes, semicircular canals, cochlear nerve and cochlea. (right) A woman holding a microphone belts out a song.
Both humans and machines use sound sensors to gather information from sound waves.
Copyright © (left) 2011 baholfor, Wikimedia Commons; (middle) 2012 Chittka L, Brockmann, Wikimedia Commons; (right) 2004 Microsoft Corporation, One Microsoft Way, Redmond, WA 98052-6399 USA. All rights reserved. http://commons.wikimedia.org/wiki/File:Lego_Mindstorms_Sound_Finder.jpg http://commons.wikimedia.org/wiki/File:10.1371_journal.pbio.0030137.g001-L-A.jpg http://office.microsoft.com/en-us/images/results.aspx?qu=singing&ex=1#ai:MP900409066|mt:2|


Students learn about how sound sensors work, reinforcing their similarities to the human sense of hearing. They look at the hearing process—sound waves converted to electrical signals sent to the brain—through human ear anatomy as well as sound sensors. A mini-activity, which uses LEGO® MINDSTORMS® NXT intelligent bricks and sound sensors gives students a chance to experiment with the sound sensors in preparation for the associated activity involving the sound sensors and taskbots. A PowerPoint® presentation explains stimulus-to-response pathways, sensor fundamentals, the unit of decibels, and details about the LEGO sound sensor, including how readings are displayed and its three modes of programming sound input. Students take pre/post quizzes and watch a short online video. This lesson and its associated activity enable students to appreciate how robots can take sensor input and use it to make decisions to via programming.
This engineering curriculum meets Next Generation Science Standards (NGSS).

Engineering Connection

Sound sensors—called auditory sensors by engineers—are used in many devices that we use every day. The stimulus-to-response pathways seen in electronic sound sensor operation mimics the human body process that involves our ears and signal transmission to the brain. Microphones are the sound sensors used in phones, computers, baby monitors and music systems like karoke machines. The use of sensors has exploded into the design of uncountable every day tools, equipment, appliances and devices.

Pre-Req Knowledge

Learning Objectives

After this lesson, students should be able to:

  • Describe how sound sensors work.
  • Compare the sound sensor to the human ear.
  • Program the LEGO MINDSTORMS NXT robot with the sound sensor
  • Provide a basic explanation of how sensors are integrated into robots via careful programming.

More Curriculum Like This

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Students learn more about how color sensors work, reinforcing their similarities to the human sense of sight. This lesson and its associated activity enable students to gain a deeper understanding of how robots can take sensor input and use it to make decisions via programming.

How Does an Ultrasonic Sensor Work?

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What Is a Sensor?

Students gain a rigorous background in the primary human "sensors," as preparation for comparing them to some electronic equivalents in the associated activity. Students learn the concept of "stimulus-sensor-coordinator-effector-response" to describe the human and electronic sensory processes.

Elementary Lesson

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

  • Use argument supported by evidence for how the body is a system of interacting subsystems composed of groups of cells. (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Gather and synthesize information that sensory receptors respond to stimuli by sending messages to the brain for immediate behavior or storage as memories. (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Various relationships exist between technology and other fields of study. (Grades 3 - 5) Details... View more aligned curriculum... Do you agree with this alignment?
  • Knowledge gained from other fields of study has a direct effect on the development of technological products and systems. (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment?
  • Describe how new technologies have helped scientists make better observations and measurements for investigations (e.g., telescopes, magnifiers, balances, microscopes, computers, stethoscopes, thermometers) (Grade 4) Details... View more aligned curriculum... Do you agree with this alignment?
  • Describe how new technologies have helped scientists make better observations and measurements for investigations (e.g., telescopes, electronic balances, electronic microscopes, x-ray technology, computers, ultrasounds, computer probes such as thermometers) (Grade 5) Details... View more aligned curriculum... Do you agree with this alignment?
  • Explain the interactions between the nervous and muscular systems when an organism responds to a stimulus (Grade 8) Details... View more aligned curriculum... Do you agree with this alignment?
Suggest an alignment not listed above


(Be ready to show students the 19-slide How Does a Sound Sensor Work? Presentation, a Microsoft® PowerPoint® file, to teach the lesson, as well as a computer/projector with Internet access to show a short online video. In advance, make copies of the Sound Sensor Pre/Post Quiz, two each per student, provided as attachments and slides. For a mini-activity, student pairs use LEGO robot components to experiment with sound sensors.)

How does the human ear work? How does the LEGO sound sensor work? Today we will review how the human ear works and then ask: What is sound? Your ears are able to take in all the sounds around us and make sense of them. In a similar way, sound sensors designed by engineers also sense sounds. Today you will measure sound levels using the LEGO brick and a LEGO sound sensor. In the next class, you get to program LEGO robots to take in sensor input and use it to make decisions to move.

(Continue by showing the presentation and delivering the content in the Lesson Background section.)

Lesson Background and Concepts for Teachers

Present the lesson using the content provided in the slide presentation, as described below. During the lesson, students engage in a mini-activity (slide 14) that requires the following for each student pair:

How Does a Sound Sensor Work? Presentation Outline (Slides 1-8)

  • Administer the pre-quiz by handing out paper copies; the quiz is also on slide 2. The answers are provided for the teacher on slide 3 for discussion after students have completed the quiz.
  • Inform students that the lesson focuses on sound sensors, both human and robotic.
  • Start with a review of human ear anatomy by showing the diagram on slide 4. Then question students to see if they know how sound is transmitted from the ear to the brain. Tell them that the details related to this will be covered next.
  • Then present details of how humans hear sounds (slides 5-6), emphasizing the structure, sound wave transmission through the various ear parts, and how sound waves are converted to electrical signals and transmitted to the brain. Then show students a two-minute "How the Ear Works" online video that summarizes all this information (link on slide 6).
  • Review the stimulus-to-response process of the human ear, using the example and explanation on slide 7 (hearing thunder-to-running for shelter). Then give students a few minutes to come up with the elements of a "stimulus-sensor-coordinator-effector-response" framework using a robot sound sensor. An example answer is on slide 18. After students have thought about it and written their answers, review the example answer with the class. Although this is summary of what has been covered so far, make sure students understand the stimulus-to-response framework.
  • Before explaining the robot sensors discussed in slide 8, question students to see if they know how many and which human senses have been duplicated in robots. Briefly explain the various sensors provided with the LEGO NXT robot kit (touch, sound, light, ultrasonic).

What Is Sound and How Can You Sense It? Presentation Outline (Slides 9-19)

  • Review the concept of sound and how it is picked up by the diaphragm in sound sensors (slide 9), how microphones do it (slide 10), and then show images of a microphone and a LEGO sound sensor side-by-side (slide 11) so students can see that they are similar since both have a diaphragm that can pick up air vibrations. Microphones can sense sound level and frequency; the LEGO sound sensor can only sense sound level.
  • (slide 12) Explain that sound sensors are also called auditory sensors. Show where the diaphragm is located on the LEGO sound sensor (under the orange foam).
  • (slide 13) Explain that the unit of measure for sound level is decibels (dB) and provide some examples. More specifically, explain that a NXT sound sensor detects sound levels up to 90 DB and displays them as a percentage of sound the sensor is capable of reading.
  • (slide 14) Next, introduce a 5-10-minute mini-activity that gives students a chance to experience how the sound sensor works. To do this, give student pairs each a LEGO brick, cable and LEGO sound sensor. Have them follow the slide instructions to attach them together and practice speaking into the sound sensor and seeing the sound reading on the brick display. Remind them that the sound sensor measures sound level as a percentage of a maximum value, and it does not measure frequency or pitch. Have them record their observations on paper. As time permits, have them try the "Try Me" option.
  • (slide 15) Explain the three different ways (modes) the LEGO sound sensor can be used through NXT programming. Three different programming blocks provide options for logical (true/false), wait and switch signaling. While not using this information as part of the lesson, it will be very helpful for students to know when developing their own programs in the associated activity.
  • Administer the post-quiz by handing out paper copies; the quiz is also on slide 16. The answers are provided on slide 17. Slide 18 lists some vocabulary terms and definitions. Next, conduct the associated activity.


auditory: Related to hearing.

sensor: A device that converts one type of signal to another; for instance, the speedometer in a car collects physical data and calculates and displays the speed the car is moving.

transducer: Another term for a sensor.

ultrasonic: A sound of a frequency that humans cannot hear, but dogs and bats can.

Associated Activities

  • Control Using Sound - Students program LEGO MINDSTORMS NXT robots to respond and move to the sound of hand claps. This activity reinforces the concepts related to sound and how sound sensors function.

Lesson Closure

The human ear has a diaphragm that vibrates when it receives sound (air pressure vibrations) and this vibration is converted to electrical signals that are conveyed to the brain. Using this idea, engineers have created sound sensors like the LEGO NXT sound sensor. The sound sensor works in a similar way to human sound sensing; it has a diaphragm that converts air pressure vibrations into electrical signals that are conveyed to the NXT brick/computer. Microphones work this way, too.



Pre-Lesson Assessment

Pre-Quiz: Before starting the lesson, administer the three-question Sound Sensor Pre/Post Quiz by handing out paper copies or showing slide 2. Students' answers reveal their base understanding of the topic. Answers are provided on the Sound Sensor Pre/Post Quiz Answer Key or slide 3. Administer the same quiz at lesson end.

Post-Introduction Assessment

Sound Sensor Mini-Activity: Observe student pairs as they experiment with the LEGO sound sensor during the mini-activity described on slide 14. Make sure groups are able to follow the slide instructions and question individual students to verify that they understand how the sound sensor works.

Lesson Summary Assessment

Post-Quiz: Administer the Sound Sensor Pre/Post Quiz again (also on slide 16), comparing students' answers with their pre-quiz answers to assess what they learned during the lesson. Quiz answers are provided in the Sound Sensor Pre/Post Quiz Answer Key (and slide 17).

Additional Multimedia Support

How the Ear Works, BupaHealth, YouTube (2:02 minutes): https://www.youtube.com/watch?v=-bKy02f1pD4&feature=youtu.be&src_vid=ahCbGjasm_E&feature=iv&annotation_id=annotation_1543119125

NXT robots and sensors: http://mindstorms.lego.com/eng/Overview/default.aspx

What is a transducer? http://en.wikipedia.org/wiki/Transducer

What is a sensor? http://en.wikipedia.org/wiki/Sensors

List of sensors: http://en.wikipedia.org/wiki/List_of_sensors

The Ear, Neuroscience for Kids: http://faculty.washington.edu/chudler/bigear.html

How Hearing Works (3:08-minute video), Med-EL Kid's Corner: http://www.medel.com/us/How-Hearing-Works

Hearing Direction and Distance by Ron Kurtis: http://www.school-for-champions.com/senses/hearing_direction.htm#.Uu2duvldUnE

How Your Ears Work, Kid's Health, Women's and Children's Health Network: http://www.cyh.com/HealthTopics/HealthTopicDetailsKids.aspx?p=335&np=152&id=1463


Srijith Nair, Pranit Samarth, Satish S. Nair


© 2013 by Regents of the University of Colorado; original © 2013 Curators of the University of Missouri

Supporting Program

GK-12 Program, Computational Neurobiology Center, College of Engineering, University of Missouri


This curriculum was developed under National Science Foundation GK-12 grant no. DGE 0440524. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.

Last modified: July 20, 2017