Basic:
* Phone: A device for transmitting and receiving sound.
* Phonics: A method of teaching reading by associating sounds with letters.
* Phonetic: Relating to the sounds of speech.
* Phonology: The study of sounds in a language.
* Phonogram: A written symbol representing a sound.
Less common but still related:
* Euphony: A pleasing combination of sounds.
* Cacophony: A harsh, discordant mixture of sounds.
* Microphone: A device for converting sound into electrical signals.
* Telephone: A device for transmitting sound over long distances.
* Homophone: Words that sound alike but have different meanings.
* Polyphony: Music with multiple independent melodic lines.
* Symphonic: Characterized by harmony and multiple instrumental parts.
* Phoneme: A basic unit of sound in a language.
Scientific:
* Phonon: A quantum of sound energy.
* Photophone: A device for transmitting sound using light.
* Sonophoresis: The use of ultrasound to enhance the penetration of substances into the skin.
Other:
* Phonograph: A device for recording and reproducing sound.
* Phonological: Relating to phonology.
* Phonetician: A specialist in phonetics.
This is not an exhaustive list, but it gives you a good starting point for exploring words with the "phon" root.