The Audio Analyzer Interactive is an adjustable-size file that displays nicely on smart phones, on tablets such as the iPad, on Chromebooks, and on laptops and desktops. The size of the Interactive can be scaled to fit the device that it is displayed on. The compatibility with smart phones, iPads, other tablets, and Chromebooks make it a perfect tool for use in a 1:1 classroom.

 

Data collection interfaces for the science classroom are more than a luxury than they are commonplace tools for most schools. The cost of outfitting a science lab to have motion detectors, force probes, light sensors, microphone/amplifiers, voltmeters and ammeters, magnetic field sensors, etc. is so prohibitive that many schools feel fortunate to just have a set up for classroom demonstrations. Fortunately, there are some tools that no longer need to be purchased. Web technologies and improved hardware allow developers to create interfaces that rely on the camera and microphone of a device like a phone, tablet, Chromebook, laptop, or desktop computer to collect authentic data. This is the case with Audio Analyzer.

Audio Analyzer uses the input from a device microphone to collect a sample of sound and display the data as both an FFT (fast-Fourier transform) display and an Oscilloscope display. The interface allows students to quickly acquire time data for the various peaks of the Oscilloscope display and calculate a period and a frequency. To use Audio Analyzer, you will have to allow The Physics Classroom access to the microphone. This is a standard security question on most operating systems whenever an application like the browser requests access to a system-level resource such as the microphone or camera. We assure users that the only reason for needing access to the microphone is to capture and analyze the sound input. We are not listening to your conversations; we are neither interested in that nor do we have the time to do it. Trust us. We're Physics teachers.

We have a few confessions to make that are of a technical nature. The first pertains to the Oscilloscope display. We are not really converting the microphone input directly to an oscillscope display. We're cheating just a bit. The code is looking for a few frequency peaks in the microphone input and then creating a wave form that is consistent with the major frequencies found in the sound sample. It does so quite quickly. Our strategy serves to filter out a lot of the noise in the data and present students with a rather clean looking signal on the oscilloscope. The signal is never going to be a low quality signal because of this strategy of filtering out the noise and creating a signal solely from the primary frequencies that are detected.

The precision of the tool is limited to the sample rate. As a result there may be a lack of precision in the frequency values. A 512 Hz tuning fork might be detected as a 514 Hz tuning fork.

Our final confession pertains to the reported pressure value. There is no reason to expect it to be an accurate measurement of the pressure. We expect Audio Analyzer to be used on a large range of microphones from phones to desktop computers. We are collecting voltage values from those microphones and using an average microphone sensitivity rating to convert the voltage to a pressure value. The only way to have an accurate pressure reading is to sell our own microphone and to use a calibration file. That's not our business; we don't sell hardware. So if you're looking to measure pressure, you will need to purchase an external microphone from a supplier and use it to capture sound. But if you're looking to analyze the rate at which the pressure changes with respect to time (i.e., frequency and period of a sound wave), our tool does an exceptional job of it for free.

One final technical detail: Audio Analyzer supports the ability to detect 0 - 6000 Hz on its FFT display, and up to 8000 Hz in the oscilloscope display.  


The Physics Classroom has prepared a student activity for use with this Interactive. It is titled Period and Frequency of a Tuning Fork.  In the activity, students capture the sound of a vibrating tuning fork and use the oscilloscope display to determine the period and the frequency of the tuning fork. The activity provides great practice with using time data for several cycles of vibration in order to calculate T and f. We suspect that teachers can find several other activities among the resource listing below to make a great lesson on the properties of sound waves.

 

There are numerous resources at The Physics Classroom website that serve as very complementary supports for the Audio Analyzer Interactive. These include:

 

 

Additional resources and ideas for incorporating the Audio Analyzer Interactive into an instructional unit on Waves and Sound can be found at the Teacher Toolkits section of The Physics Classroom website.  Visit Teacher Toolkits.

 

 

 

We owe a special thanks to Physics and Chemistry teacher Chris Bruce (Nerd Island Studios | SimBucket) for creating this Interactive.