Bass or Treble? Measure the Frequency Response of a Speaker *
|Areas of Science||
Technology of Art
|Time Required||Average (6-10 days)|
|Material Availability||Specialty electronics items required.|
|Cost||Average ($40 - $80)|
|Safety||Always keep speaker volume at safe levels to avoid hearing damage.|
Whether you have already tried the Science Buddies Build a Paper Speaker activity or the How Loud Can Paper Speakers Get? project, or you just like music and are interested in exploring more about the science of sound, then this project is for you.
You probably know that sound waves can have different frequencies. If not, you can read more about that in the background section of the How Loud Can Paper Speakers Get? project. The range of human hearing is typically about 20 hertz (Hz) to 20,000 Hz. Frequencies at the lower end of this range are typically referred to as bass, the higher end is called treble, and those in the middle are called mid-range. Ideally, a single speaker would be able to play sounds at all frequencies "equally," meaning it would not make certain frequencies sound louder than others. However, this is not the case. Many times speakers are separated into tweeters for playing high frequencies and woofers for playing low frequencies. Why is this necessary?The reason has to do with a concept called resonant frequency, sometimes called "natural frequency." Every mechanical system or object has a natural frequency at which it "likes" to vibrate. In general, smaller, lighter, and stiffer objects like to vibrate faster than bigger, heavier, and softer objects. For example, imagine "pinging" a small metal object (like a ruler or paperclip) by flicking it with your finger. It will vibrate back and forth very quickly—possibly faster than your eye can see. Now, think about much larger objects, like tree branches swaying in the wind; they rock back and forth very slowly. The same concept applies to speakers—smaller, lighter tweeters will vibrate at higher frequencies, while larger, heavier woofers will vibrate at lower frequencies.
A graph of the amplitude of a vibration versus the frequency of the vibration is called a system's frequency response. A good speaker should have a frequency response that is as "flat" as possible, meaning it reproduces frequencies at the same volume at which they were recorded. Otherwise, large peaks or valleys in the frequency response will result in some frequencies sounding much louder or quieter than others. Figure 1 shows an example frequency response for a set of computer speakers.
Figure 1. Frequency response for a pair of computer speakers. Notice that the x-axis of a frequency response is typically plotted using a logarithmic scale, due to the large range of frequencies for human hearing.
There are many science projects you can do involving the frequency response of speakers. Here are just a few ideas:
- Build your own paper speaker, like in the Science Buddies project How Loud Can Paper Speakers Get? Measure the frequency response by playing tones at different frequencies and recording the volume in decibels (dB) (the procedure for doing this at a single frequency is described in the project), and produce a graph like Figure 1. How flat is the speaker's frequency response? Would you characterize the speaker as a tweeter, a woofer, or a mid-range speaker?
- Investigate how different variables can change the frequency response of a paper speaker. Remember that natural frequency is controlled by the stiffness and mass of an object. What can you change about the basic design of a paper speaker to alter its frequency response? Can you design and build speakers with two distinct frequency responses, one tweeter and one woofer?
- If you have a home stereo system, see if you can look up the frequency response data for the speakers from the manufacturer. Do your own experiments to measure the frequency response. Do your results line up with the manufacturer's claims?
Cite This PageGeneral citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.
Last edit date: 2018-03-15
- Mitchel, M. (2005, April 9). Understanding Speaker Frequency Response. Ecoustics. Retrieved September 25, 2015 from http://www.ecoustics.com/articles/understanding-speaker-frequency-response/
- ht-aduio.com. (n.d.). How a Speaker Works. Retrieved September 25, 2015 from http://www.ht-audio.com/pages/SpeakerBasics.html
- Henderson, T. (n.d.). Sound Waves and Music. The Physics Classroom. Retrieved September 25, 2015 from http://www.physicsclassroom.com/class/sound
News Feed on This Topic
Ask an ExpertThe Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.
Ask an Expert
If you like this project, you might enjoy exploring these related careers:
Electrical & Electronics EngineerJust as a potter forms clay, or a steel worker molds molten steel, electrical and electronics engineers gather and shape electricity and use it to make products that transmit power or transmit information. Electrical and electronics engineers may specialize in one of the millions of products that make or use electricity, like cell phones, electric motors, microwaves, medical instruments, airline navigation system, or handheld games. Read more
Sound Engineering TechnicianAny time you hear music at a concert, a live speech, the police sirens in a TV show, or the six o'clock news you're hearing the work of a sound engineering technician. Sound engineering technicians operate machines and equipment to record, synchronize, mix, or reproduce music, voices, or sound effects in recording studios, sporting arenas, theater productions, or movie and video productions. Read more
Audio and Video Equipment TechnicianEver wondered who makes sure the Jumbotron works at the super bowl? Or that the microphones work at a presidential inauguration? These are the tasks of an audio and video equipment technician. Audio and video equipment technicians work to set up and operate audio and video equipment, including microphones, sound speakers, video screens, projectors, video monitors, and recording equipment. Read more
News Feed on This Topic
Looking for more science fun?
Try one of our science activities for quick, anytime science explorations. The perfect thing to liven up a rainy day, school vacation, or moment of boredom.Find an Activity
Explore Our Science Videos
How to Make an Archimedes Screw - STEM Activity
Physics and Chemistry of an Explosion Science Fair Project Idea
How to make an anemometer (wind speed meter)