Clicks when starting the envelope

[thomastanck]

Image of waveform in Audacity

I'm getting clicks at the start of every sound. This is the code I'm using atm, on Firefox 49.0, OS X (El Capitan).

    var cumT = this.audioCtx.currentTime;
    var oscillator = this.audioCtx.createOscillator();
    oscillator.type = 'sine';
    oscillator.frequency.value = this.wave.frequency;
    var gain = this.audioCtx.createGain();
    var volume = this.audioCtx.createGain();
    oscillator.connect(gain);
    gain.connect(volume);
    volume.gain.value = 0.5;
    volume.connect(this.audioCtx.destination);
    oscillator.start(cumT);
    var stopAt = cumT;
    for (var t = 0; t < timings.length; t += 1) {
        var duration = timings[t] / 1000;
        if (duration > 0) {
            // oscillator.connect(this.audioCtx.destination);
            var env = new Envelope(this.audioCtx, {
                    // curve: "exponential",
                    attackTime: 0.03,
                    // decayTime: 1.0,
                    sustainLevel: 1.0,
                    releaseTime: 0.03,
                    startLevel: 0.0
                });
            gain.gain.value = 0;
            env.connect(gain.gain);
            gain.gain.value = 0;
            env.start(cumT);
            cumT += duration;
            // oscillator.stop(cumT);
            env.release(cumT);
            stopAt = env.getReleaseCompleteTime();
            env.stop(stopAt);
        } else {
            cumT += -duration;
        }
    }
    oscillator.stop(stopAt);

Any idea how to solve this?