Detect frequencies in a buffer along the time

Question

if I record a series of frequencies beeps into a buffer, for example:

15kHz for 50ms, 17k for 50 ms and goes on, is there any way to "go" along the time plain and to decode this freqs(with goertzel or something)?

Hey, this is an update, I've added a code that shows how I find the first delimiter in the sound buffer that I check. If I record 5 seconds of a buffer(I record into a stream buffer and not a file) The first snippet takes something like 30 seconds to analyze the index where the start delimiter starts at. I thinks it is very newbie...must find a better solution. thanks (every delimiter is 0.2 seconds duration) and it's like that - Start delimiter = 12KHz, 1's = 13k, 0's = 14k, End delimiter = 15k

        double max_power = 0;
        int max_power_index = 0;
        double DelimiterSamplesCount = SampleRate * DelimiterTime;
        float[] samples32array = samples32.ToArray();

        //Searching For Delimiter
        for (int i = 0; i < (samples32array.Length); i++) //Delimiter Samples Length = SampleRate*DelimiterTimeLength,( i.e: 44100*0.2=8820 samples)
        {
            if ((i + (int)DelimiterSamplesCount - 1) > samples32array.Length) break;
            double power = Goertzel.GoertzelFilter(samples32array, StartDelimiterFreq, i, i + (int)DelimiterSamplesCount - 1);
            if(power > max_power)
            {
                max_power = power;
                max_power_index = i;
            }
        }

My Goertzel is like that:

public static double GoertzelFilter(float[] samples, double freq, int     start, int end)
    {
        double sPrev = 0.0;
        double sPrev2 = 0.0;
        int i;
        double normalizedfreq = freq / 44100;
        double coeff = 2 * Math.Cos(2 * Math.PI * normalizedfreq);
        for (i = start; i < end; i++)
        {
            double s = samples[i] + coeff * sPrev - sPrev2;
            sPrev2 = sPrev;
            sPrev = s;
        }
        double power = sPrev2 * sPrev2 + sPrev * sPrev - coeff * sPrev * sPrev2;
        return power;
    }

Answer 1

If you know the set of frequencies and the durations, then a set of sliding Goertzel filters is a good start to building a simple demodulator. Comparing and scanning for for a peak difference between these filters is a better decision criteria than just checking for a certain magnitude output.