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Our group, used GNU radio which is a platform that allows us to analyze  and process the data we received from our horn telescopes and the 40 ft telescope. When the telescopes collect data, it's all analog. We attached an AIRSPY Software Defined Radio to convert the signal from analog to digital, and GNU radio to interpret the data from the telescope so that we could analyze it. Below you'll see an image of the file that was created to filter and process the spectrum. The next picture shows the difference between a filtered signal and an unfiltered signal from the telescropes.

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With a partner you will reveal several messages from popular movies, TV, and music. You will have to apply band-pass and notch filters to the spectrum to uncover the signal. You don't have to go in order. Write down what you think the messages say. Put on headphones
http://gbofiltering.bitballoon.com/

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The resulting signal

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The original signal with a a notch filter applied to it.

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The original signal with a band-pass filter applied

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The resulting signal

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Coffee Filters keep chunks of coffee grinds from getting into your cup of coffee

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Applying a filter to a photo can help to make it less grainy or change the coloring of the image. (Think Instagram or SnapChat filters)

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Noise cancelling headphones play a tone that is the exact opposite of the noise in the immediate area so that all or most of the noise is cancelled.

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Water filters are placed on the water taps or in water dispensers to filter impurities.

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Filters block out any information that would otherwise distract us from seeing what we want. Think about when it's really noisy and you're trying to hear someone, what do you do? You turn off some of the things that are making noise or remove yourself from a noisy environment. When we filter a signal, we essentially do the same thing. We are taking out all the noise so that we can hear what we need to hear and not all the things that we don't.

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band-pass filter: A filter that only keeps a certain range of frequency components and blocks any other frequencies outside the range.

frequency: How many times a waveform repeats per second, measured in hertz. Hz = cycles per second

high-pass filter: A filter that keeps high-frequency components and blocks low-frequency components.

low-pass filter: A filter that keeps low-frequency components and blocks high-frequency components.

noise: Any component of a signal that does not contain useful information.

notch filter: A filter that blocks specific frequency points and does not affect the rest of the signal.

courtesy of TeachEngineering
https://www.teachengineering.org/lessons/view/csm_filtering_lesson01

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The band-pass filter is set to around 400 to 2300 Hz with six notch filters at around 900 Hz, 1100 Hz, 1300 Hz, 1500 Hz, 1700 Hz and 1900 Hz. Once filters are added to remove all the noise in the signal, students may need to turn the volume up further to hear the message.