A JavaScript file to generate sounds procedurally on any browser by generating WAV files as data URI

sound.js

// This function only generates pure frequencies but you can customize the waveform
// by changing the function at line ~50 (the one with the cos)

function sound(freq,volume,duration,fadeout){
	// Generate a wav binary file, convert it to a blob and play it.
	// https://fr.wikipedia.org/wiki/Waveform_Audio_File_Format#Structure_des_fichiers_WAV

	const sampling = 44100; // in hertz
	duration = duration || 1; // in seconds
	const sampleCount = Math.floor(sampling * duration);

	volume = volume || 0.5;
	if(volume > 1) volume = 1;
	if(volume < 0) volume = 0; // clamp
	volume = Math.floor(volume * 256 * 256); // convert to 16 bit integer

	freq = freq || 440; // nice default freq 

	// Helper function to build binary files
	function toBytes(value, bytes) {
		let result = "";
		for (; bytes>0; bytes--) {
			result += String.fromCharCode(value & 255);
			value >>= 8;
		}
		return result;
	}

	let samples = "";

	// Example of a fade: linear fade.
	// fadeout = fadeout || ((t,max) => (max-t)/max);

	// By default, be use a fancy "fast attack, slow descent" fade
	fadeout = fadeout || ((t,max) => {
		const attackRatio = 0.01;
		if(t/max < attackRatio){
			// fast attack
			return t/max/attackRatio;
		}else{
			// slow descent (linear)
			return (1-(t/max)) / (1-attackRatio);
		}
	});

	for(let i = 0;i < sampleCount;i++){
		samples += toBytes(
			(Math.cos(
				2 * Math.PI * i * freq / sampling
			)+1)/2 * volume * fadeout(i,sampleCount)
		,2);
	}


	let dataChunk = [
		"fmt ",
		"\x10\x00\x00\x00", // 16: chunk length
		"\x01\x00", // audio format, PCM integer
		"\x01\x00", // mono
		toBytes(sampling,4),
		toBytes(sampling * 2,4), // bytes / sec
		"\x02\x00", // bytes per bloc
		"\x10\x00", // bytes per sample
		"data",
		toBytes(sampleCount * 2,4),
		samples
	].join('');


	let wav = [
		"RIFF",
		toBytes(20 + dataChunk.length,4),
		"WAVE",
		dataChunk
	].join('');

	let uint8 = new Uint8Array(wav.length);
	for(let i = 0; i < uint8.length; i++) {
		uint8[i] = wav.charCodeAt(i);
	}


	let blob = new Blob([uint8], {type: 'audio/wav'});
	let audioObject = new Audio();
	audioObject.src = URL.createObjectURL(blob);
	audioObject.play();
	return audioObject;
}