Find nearest zero crossing in waveform after frame ``n``

def zero_crossing_after(self, n):
        """Find nearest zero crossing in waveform after frame ``n``"""
        n_in_samples = int(n * self.samplerate)
        search_end = n_in_samples + self.samplerate
        if search_end > self.duration:
            search_end = self.duration

        frame = zero_crossing_first(
            self.range_as_mono(n_in_samples, search_end)) + n_in_samples

        return frame / float(self.samplerate)