Large meteoroids in the Lyrid stream

The outburst of the Lyrid meteor shower in 1803 was remarkable for being ri ch in bright fireballs and the generation of electrophonic sounds. The impl ications implicit to the detection of electrophonic sounds are studied in t his paper. We present estimates for the minimum-sized Lyrid meteoroid capab le of generating electrophonic sounds, and compare these lower limits with the largest meteoroid that might reasonably be ejected from a cometary nucl eus through coupling with the sublimation gas outflow. A difference of a fa ctor of order 30 is found between the two limiting sizes. A minimum diamete r of order Im is required for a Lyrid meteoroid to satisfy the conditions n ecessary for generating electrophonic sounds. The mechanisms responsible fo r the placement of large, metre-sized meteoroids into the Lyrid stream are not well defined, but they possibly relate to surface ageing effects of the parent comet, Comet C/1861 G1 Thatcher, and to a history of nuclear fragme ntation.