The JACK API implements an audio server, allowing the connection of various software clients and hardware interfaces. In short, it turns the whole system into a digital audio workstation (DAW). It is the pro audio standard on Linux systems, but is also available for Mac and Windows.
Qjackctl with hardware connections and two clients.
Wavefolding is a speacial case of waveshaping, working with periodic transfer functions. The following example calculates the spectrum of a sinusoidal function, folded with a sinusoidal transfer function.
Sinusoidal Wavefolder Sine Example.
Frequency Gain
Time Domain:Frequency Domain:
Waveshaping adds overtones to a signal by means of distortion.
This first, simple Web Audio sonification application makes use of the Weather API for real-time, browser-based sonification of weather data. For fetching data, a free subscription is necessary: https://home.openweathermap.org
Once subscribed, the API key can be used to get current weather information in the browser:
https://api.openweathermap.org/data/2.5/weather?q=Potsdam&appid=eab7c410674e15bfdd841f66941a92c2
The resulting output in JSON looks like this:
{ "coord": { "lon": 13.41, "lat": 52.52 }, "weather": [ { "id": 804, "main": "Clouds", "description": "overcast clouds", "icon": "04d" } ], "base": "stations", "main": { "temp": 9.74, "feels_like": 6.57, "temp_min": 9, "temp_max": 10.56, "pressure": 1034, "humidity": 93 }, "visibility": 8000, "wind": { "speed": 4.1, "deg": 270 }, "clouds": { "all": 90 }, "dt": 1604655648, "sys": { "type": 1, "id": 1275, "country": "DE", "sunrise": 1604643143, "sunset": 1604676458 }, "timezone": 3600, "id": 2950159, "name": "Berlin", "cod": 200 }
All entries of this data structure can be used as synthesis parameters in a sonification system with Web Audio.
In this example we are using a simple freuency modulation formula for turning temperature and humidity into more or less pleasing (annoying) sounds. The frequency of a first oscillator is derived from the temperature:
\(\displaystyle f_1 = 10 \frac{1}{{T^2 / C^{\circ} }}\)
The modulator frequency is controlled by the humidity \(H\):
\(y = sin(2 \pi (f_1 + 100*sin(2 \pi H t))t)\)
The resulting app fetches the weather data of a chosen city, extracts temperature and humidity and sets the parameters of the audio processes:
What does the weather sound like in ...?
<!doctype html> <html> <head> <title>Where would you rather be?</title> </head> <blockquote style="border: 2px solid #122; padding: 10px; background-color: #ccc;"> <body> <p>What does the weather sound like in ...?</p> <p> <button onclick="myFunction()">Enter City Name</button> <button onclick="stop()">Stop</button> <p id="demo"></p> </p> </body> <div id="location"></div> <div id="weather"> <div id="description"></div> <h1 id="temp"></h1> <h1 id="humidity"></h1> </div> </blockquote> <script> var audioContext = new window.AudioContext var oscillator = audioContext.createOscillator() var modulator = audioContext.createOscillator() // the output gain var gainNode = audioContext.createGain() var modInd = audioContext.createGain(); modInd.gain.value = 100; gainNode.gain.value = 0 modulator.connect(modInd) modInd.connect(oscillator.detune) oscillator.connect(gainNode) gainNode.connect(audioContext.destination) oscillator.start(0) oscillator.frequency.setValueAtTime(100, audioContext.currentTime); modulator.start(0) modulator.frequency.setValueAtTime(100, audioContext.currentTime); function myFunction() { var city = prompt("Enter City Name", "Potsdam"); if (city != null) { get_weather(city) } } function stop() { gainNode.gain.linearRampToValueAtTime(0, audioContext.currentTime + 1); } function frequency(y) { oscillator.frequency.value = y } function get_weather( cityName ) { var key = 'eab7c410674e15bfdd841f66941a92c2'; fetch('https://api.openweathermap.org/data/2.5/weather?q=' + cityName+ '&appid=' + key) .then(function(resp) { return resp.json()}) // Convert data to json .then(function(data) { setSynth(data); }) .catch(function() { // catch any errors }); } function setSynth(d) { var celcius = Math.round(parseFloat(d.main.temp)-273.15); var fahrenheit = Math.round(((parseFloat(d.main.temp)-273.15)*1.8)+32); var humidity = d.main.humidity; oscillator.frequency.linearRampToValueAtTime(1000*(100/(celcius*celcius)), audioContext.currentTime + 1); modulator.frequency.linearRampToValueAtTime(humidity, audioContext.currentTime + 1); gainNode.gain.linearRampToValueAtTime(1, audioContext.currentTime + 1); document.getElementById('description').innerHTML = d.weather[0].description; document.getElementById('temp').innerHTML = celcius + '°'; document.getElementById('location').innerHTML = d.name; document.getElementById('humidity').innerHTML = 'Humidity: '+humidity; } </script> </html>
Using the API in JavaScript is thoroughly explained here: https://bithacker.dev/fetch-weather-openweathermap-api-javascript
NASA offers a great variety of open APIs with data from astronomy: https://api.nasa.gov/
The quarantine sessions are an ongoing concert series between CCRMA at Stanford, the TU Studio in Berlin, the Orpheus Institute in Gent, Belgium and various guests:
https://hvc.berlin/projects/quarantine-sessions/
These sessions use the same software components as the SPRAWL System. Audio is transmitted via Jacktrip and SuperCollider is used for signal processing.
The Electronic Orchestra Charlottenburg (EOC) was founded at the TU Studio in 2017 as a place for developing and performing with custom musical instruments on large loudspeaker setups.
EOC Website: https://eo-charlottenburg.de/
Initially, the EOC worked in a traditional live setup with sound director. Several requests arose during the first years:
During Winter Semester 2019-20 Chris Chafe was invited as guest professor at Audio Communication Group. In combined classes, the SPRAWL network system was designed and implemented to solve the above introduced problems in local networks:
https://hvc.berlin/projects/sprawl_system/
The official TU website with information on the schedule and assessment:
https://www.ak.tu-berlin.de/menue/lehre/wintersemester_202021/network_music_performance_systems/
The TUB cloud drive is used for additional materials like audio, scores and papers:
The repository contains SHELL scripts, SuperCollider code and configuration files for the server and the clients of the SPRAWL system:
Jacktrip is the open source audio over IP software used in the SPRAWL system:
https://github.com/jacktrip/jacktrip
The Faust oscillators.lib comes with many different implementations of oscillators for various waveforms. At some point one might still need a behavior not included and lower level approaches are necessary.
This example shows how to use a phasor to read a wavetable with a sine waveform. This implementation has an additional trigger input for resetting the phase of the oscillator on each positive zero crossing. This can come handy in various applications, especially for phase-sensitive transients, as for example in kick drums.
The example is derived from Barkati et. al (2013) and part of the repository:
import("stdfaust.lib"); // some basic stuff sr = SR; twopi = 2.0*ma.PI; // define the waveform in table ts = 1<<16; // size = 65536 samples (max of unsigned short) time = (+(1) ~ _ ) , 1 : - ; sinewave = ((float(time) / float(ts)) * twopi) : sin; phase = os.hs_phasor(ts,freq,trig); // read from table sin_osc( freq) = rdtable(ts ,sinewave , int(phase)) ; // generate a one sample impulse from the gate trig = pm.impulseExcitation(reset); reset = button ("reset"); freq = hslider("freq", 100, 0, 16000, 0.00001); // offset = hslider("offset", 0, 0, 1, 0.00001); process = sin_osc(freq);