Add sharship noise generator

toys/index.md

@@ -5,6 +5,7 @@ title: Toys
 Here is some various junk I've done.  Maybe you'll find it amusing.
 Maybe you'll just wonder why I spend so much time on this garbage.
 
+* [Starship Noise Generator](starship.html)
 * If you need to write someone a letter but really don't want to, try my
-  [social letter generator](letter.html).
-* [Crunt](crunt.html).
+  [social letter generator](letter.html)
+* [Crunt](crunt.html)

toys/starship.md

@@ -0,0 +1,65 @@
+---
+title: Starship Noise Generator
+---
+
+<div>
+<input id="fader" type="range" min="0" max="10" step="0.01"> Gain
+</div>
+
+I work in a building with no HVAC,
+which means we can hear *everything* people are saying,
+anywhere in the building.
+
+This page is a low-CPU noise generator that runs entirely in JavaScript.
+Once it starts,
+you don't need an Internet connection to keep it going.
+You can leave it running forever, if you like.
+
+For those interested,
+it uses the new (in 2017) and seriously powerful
+[Web Audio API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Audio_API).
+
+<script>
+      function whiteNoise(audioCtx) {
+        var bufferSize = 17 * audioCtx.sampleRate,
+        noiseBuffer = audioCtx.createBuffer(1, bufferSize, audioCtx.sampleRate),
+        output = noiseBuffer.getChannelData(0);
+        for (var i = 0; i < bufferSize; i++) {
+          output[i] = Math.random() * 2 - 1;
+        }
+        var whiteNoise = audioCtx.createBufferSource();
+        whiteNoise.buffer = noiseBuffer;
+        whiteNoise.loop = true;
+        whiteNoise.start(0);
+        return whiteNoise;
+      }
+      
+      function bandpassFilter(audioCtx, freq, gain) {
+        var filt = audioCtx.createBiquadFilter();
+        filt.type = "bandpass";
+        filt.frequency.value = freq;
+        filt.gain.value = gain;
+        return filt;
+      }
+      function boop() {
+        var audioCtx = new window.AudioContext();
+        var synth = whiteNoise(audioCtx);
+        var filterA = bandpassFilter(audioCtx, 100, 20);
+        var filterB = bandpassFilter(audioCtx, 50, 20);
+        var gainA = audioCtx.createGain();
+        whiteNoise(audioCtx).connect(filterA);
+        filterA.connect(filterB);
+        filterB.connect(gainA);
+        gainA.connect(audioCtx.destination);
+        
+        function setFade() {
+          var faderPos = document.querySelector("#fader").value;
+          gainA.gain.value = faderPos;
+        }
+        setFade();
+        document.querySelector("#fader").addEventListener("input", setFade);
+      }
+      
+  
+      window.addEventListener("load", boop);
+</script>