41.   The face can even disappear to reveal the positioning of lips and tongue as sounds are produced, which might aid in learning languages.

42.   The final compositions showed small improvements in how students produced sounds and alternated instruments.

43.   The frogs are difficult to find because they produce no sound above water.

44.   The object produced no sound and was observed to change brightness, size and color, according to the report.

45.   The orchestra and conductor, hidden from view, produced a sound that seemed to spread over the width and height of the stage space.

46.   The pianist strikes a key, which moves a hammer, which hits some strings, which vibrate to produce the sound.

47.   The radio giants of the day -- RCA, Emerson, Philco and Zenith -- sniffed at these attempts to produce better sound.

48.   The state has given grants to researchers trying to come up with attachments for boats that produce sounds to alert manatees.

49.   The units are dipolar, which means that they produce sound both in front and behind equally.

50.   They try to construct mathematical and computer models of instruments, figure out how they produce the sounds they do and write programs to replicate them.