 // 4th order IIR filter.

        let nyquist = sampleRate / 2;
        // Compute the coefficients of a lowpass filter.

        // First some preliminary stuff.  Compute the coefficients of the
        // biquad.  This is used to figure out how frames to use in the test.
        let biquadType = 'lowpass';
        let biquadCutoff = 350;
        let biquadQ = 5;
        let biquadGain = 1;

        let coef = createFilter(
            biquadType, biquadCutoff / nyquist, biquadQ, biquadGain);

        // 