This story debuted with either the Second or Third Doctor, then was reprinted with the Fourth Doctor. It may have had different companions in the reprint, as well. From an in-universe point of view, it's unclear which Doctor lived through these events.
The Unheard Voice was the final outing for the Third Doctor in TV Action, cutting short the Doctor Who comic strip one issue before the demise of the magazine. TV Action would have one more story to debut, in their annual of 1974 — but this was the last regular comic strip in a series that had run almost uninterrupted since the first issue of Countdown. From here, the Third Doctor would again grace the pages of TV Comic, the traditional 1960s home of the Doctor Who comic strip.
Returning to Earth in normal space, the Doctor's flight is disturbed by a sonic weapon that seems to originate on a remote Scottish island. He lands the TARDIS there to find two seemingly unrelated things: a Ministry of Defence installation and a natural bird sanctuary that seems very much disturbed. At the installation, he is treated as a spy until his identity is confirmed by the Brigadier. He quickly determines that the new defence satellite jointly launched by the British and American defence establishments is malfunctioning, causing sound waves in a range typically only heard by animals. These waves are driving animals crazy around the planet.
Colonel Higgs, the commanding officer of the facility, finally sees that the Doctor is speaking the truth. Since his team of scientists can't correct the satellite from the ground, he comes to the view that the satellite must be destroyed. He confers with his American counterpart, who concurs. The Americans launch a missile to destroy the satellite, but its guidance system is affected by the sound waves emitted by the satellite. The remote detonation button also fails to work, so it's up to the Doctor to take the TARDIS into closer proximity. He blows up the offending machinery, returning Earth's animal population to a state of relative calm.
- The Doctor tells Colonel Higgs that his identity can be checked with "Brigadier Lethbridge-Stewart of UNIT".
- The sonic screwdriver can temporarily disrupt other sonic patterns.
- The story is a bit of social commentary on the militarisation of space — a real-life issue that grabbed headlines in the early 1970s, alongside coverage of the Apollo program.
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