code: def zero_crossing_after(self, 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)
docs: Find nearest zero crossing in waveform after frame ``n``