Hearing aid

A hearing aid, comprising:

• an external microphone configured to collect sound outside the ear canal;
• an ear canal microphone configured to collect sound inside the ear canal;
• a hearing aid processor configured to subject input sound data indicating the sound collected by the external microphone to hearing aid processing on the basis of fitting information set by fitting;
• a correction-use sound output component configured to output correction-use sound on the basis of correction-use sound data;
• an interface arranged to be operated by a user;
• a transmission characteristic calculator configured to calculate an at-fitting transmission characteristic on the basis of first sound data and second sound data when the hearing aid is set for fitting, the first sound data produced by collection at the ear canal microphone of the correction-use sound outputted from the correction-use sound output component, and the second sound data corresponding to the correction-use sound data,
• the transmission characteristic calculator configured to calculate an in-usage transmission characteristic on the basis of third sound data and fourth sound data when the hearing aid is actually used by user after the hearing aid has been set for fitting, the third sound data produced by collection at the ear canal microphone of the correction-use sound outputted from the correction-use sound output component according to user operation, and the fourth sound data corresponding to the correction-use sound data;
• a correction characteristic calculator configured to calculate a correction characteristic on the basis of the at-fitting transmission characteristic and the in-usage transmission characteristic;
• and
• a correction component configured to correct the input sound data undergone hearing aid processing by the hearing aid processor, on the basis of the correction characteristic, wherein:
• the transmission characteristic calculator is configured to calculate the at-fitting transmission characteristic on the basis of a ratio of the first sound data to the second sound data, and the in-usage transmission characteristic on the basis of a ratio of the third sound data to the fourth sound data;
• and
• the correction characteristic calculator is configured to calculate the correction characteristic on the basis of a ratio of the at-fitting transmission characteristic to the in-usage transmission characteristic.