A B757 cabin crew detected a strong electrical smell at cruise. The SMOKE/FUME Checklist as well as personal electronic devices were turned off. The smell dissipated until on final approach when the crew declared an emergency because of the smell's return.

Narrative

Flying from ZZZ1 to ZZZ. The flight was uneventful until FL400; 300 miles north of ZZZ when Flight Attendant called the cockpit to report an electrical odor in the cabin. She said there was a strong electrical smell burning their eyes; but no smoke associated with the smell. I asked her to remain on the interphone and have every available crew member look for a source. Meanwhile; we started the Smoke and Fumes Electrical checklist. Flight Attendant turned off all galley lights and the Inflight Entertainment equipment; while we turned off the recirculation fans and utility busses. We also asked all passengers to turn off any electrical equipment they might have running (computers; music; etc.) in case the smell was coming from a lithium battery. We then contacted ZZZ Dispatch and Maintenance on the VHF radio. The smell seemed to have dissipated at this point; so we reached a general consensus to continue to ZZZ and monitor the situation. Shortly after handoff to ZZZ Approach; about 15;000 FT and 40 NM north of ZZZ; Flight Attendant called us back to report the smell had returned. At that point; I declared an emergency and requested high speed direct to the airport. We accomplished the normal checklists enroute; called the airport in sight; and were granted clearance for a visual approach to Runway 26R. After landing; we exited on a high speed taxiway; told the passengers to remain seated while the Fire Department examined the aircraft. As the smell had dissipated again and there was still no indication of smoke; we elected to taxi to the gate. At the gate; we completed shutdown and secure checklists to preserve cockpit instruments. I turned on the emergency lights and assisted in deplaning. After write-ups and conferring with Maintenance; we departed for the hotel.