I should have timed the oscillation

The second non-barbed wire down on this fence at Dinorwig Quarry skips the next pole and thus spans 5 metres between nodes. That would give a 10 metre wavelength when oscillating as a stationary wave. It made a note that was inaudible. I should have timed the oscillation to get the frequency. Next time, with frequency and wavelength, I'll be able to calculate the wave speed. I can estimate the mass per unit length and thus get the tension. I need to find another fence!