There is no specific CPT code for "Pure tone audiometry (threshold); bone only". You can use the code 92553 (Pure tone audiometry (threshold); air and bone) with modifier 52.

92553

otoscopy should be done before carrying out pure tone audiometry to see if the patient has impacted cerumen which can also cause hearing problem.

Tone means something that the author uses in a book.

Pure tone and speech audiometry are two screening tests that are often used to evaluate hearing. Pure tone audiometry tests to see how well someone can hear tones of different volume and pitch