Browsed by
Month: October 2017

Infrasound processing with SoX

Infrasound processing with SoX

In this post I’ll cover how to use SoX to make low frequency sounds audible in a range that can be listened to. Infrasound is a low frequency sound wave that ranges from 20 hertz down to .1 hertz. Monitoring audio frequencies in this range is typically done to detect seismic activity that is caused either by nature or artificially, https://www.isla.hawaii.edu/sounds/ocean-sounds/. I have a sample of video that was shot with a Mobius camera. The audio range of the camera’s…

Read More Read More

Noise Filtering with SoX

Noise Filtering with SoX

In this post I’ll cover how to remove noise in an audio file using SoX. I’ll be using a Raspberry Pi which does not have an audio input by default. To get audio, I used an simple USB audio microphone to capture audio. The OS I’m running on my Pi is Ubuntu Mate and there was no need for anything to get the microphone to run. Once it was plugged in, I ran this command to view the properties of…

Read More Read More

Generating DTMF with SoX

Generating DTMF with SoX

In this post I’ll show how SoX can generate DTMF, (Dual-tone multi-frequency signaling) which is commonly used in phone and security systems. These dual tone signals are the foundation from which digital communications are based. The technology around DTMF is not complex. Lets cover the history of DTMF. DTMF was developed by Bell Labs and put in production in the early 1960’s. It was mostly used to replace pulse dialing systems that had limits on how far a phone could…

Read More Read More

SoX Noise Generation

SoX Noise Generation

In my last post I suggested creating noise and using a band of it to fill in a band gap. SoX provides a way to generate noise. There are different types of noise that SoX will generate. Lets take a moment to look at these types and what applications noise generation is used for. There are 3 main types of noise that SoX will generate, they are white, pink, and brown. White noise is a random signal that has equal…

Read More Read More

Sox Band-Pass and Band-Reject Filtering

Sox Band-Pass and Band-Reject Filtering

SoX provides many filters to process audio data. In this post I’ll be covering how to apply pass or reject filtering of frequency bands, commonly referred to as band-pass or band-reject. This filter will take a frequency or a range of frequencies and either remove them from an audio file or remove all other frequencies while keeping only them. I’ll cover 5 filters available in SoX that do this type of audio processing. Here is some information about each of…

Read More Read More