def _spec_freq_dim(sample_rate, window_size=25):
    """
    Compute the number of frequency bins of a spectrogram.

    Args:
        sample_rate : Hz of the audio.
        window_size : Size of specgram window in milliseconds.
    Returns:
        An integer representing the number of dimensions in
        the spectrogram.
    """
    return int(((sample_rate / 1000) * window_size) / 2) + 1