Obligation of offering the congregational Salah even if not hearing the Adhan except through loud speakers

A: Whoever hears the Adhan should answer the call, unless he has a Shar`y (Islamically lawful) excuse. This is indicated in what was related by Abu Hurayrah (may Allah be pleased with him), that a blind man came to the Prophet (peace be upon him) and said, O Messenger of Allah! (I am blind and) I do not have someone to lead me to the Masjid. Is there any concession for me to offer Salah at home? The Prophet (peace be upon him) said, "Do you hear the Adhan?" He said, "Yes."The Prophet said, "Then answer it." Related by Muslim in the Book of Masjids (1/458); Imam Ahmad (volume 3, p. 423); Abu Dawud, Al-Nasa'y and Ibn Majah with a slight variation. (Part No. 6; Page No. 203) The Prophet (peace be upon him) also said, Whoever hears the Adhan and does not come to Salah, then his Salah is not valid, unless he has an excuse. Related by Ibn Majah and Al-Daraqutny with a Sahih (authentic) Isnad (chain of narration). It was also related by Imam Ahmad in his Musnad (Hadith compilation) with a slight variation. When Ibn `Abbas (may Allah be pleased with him) was asked about the excuses, he said, "Either fear or sickness."May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.