A photophone consisting of a light guiding fiber, an absorption cell containing charred cotton suspended in air, an exponentially tapered tube, and a standard earpiece volume has been made and tested. The pressure in the earpiece versus the frequency in the 300–3300‐Hz telephone band for a given optical power input agrees well with the theory of the preceding paper. We conclude that the charred cotton suspended in air can be treated simply as light‐absorbing air. Measurements were also made on a photophone which included an air column equalizer to resonate with the absorption cell in order to flatten the frequency response. The high‐frequency (1500–3300 Hz) response was enhanced as expected thought not quite as much as predicted.

Subject Classification: [43]85.76, [43]85.40, [43]85.60.

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