___________________________________.When the sound reached the diaphragm by the cylinder, the pen jumped back to its original position. Because Regnault knew how far the gun was from the cylinder and how fast the cylinder turned, he calculated that sound travels through air at 750 miles per hour, quite close to the speed physicists accept today.当声音触发声敏膜片后,笔会跳回原位.由于勒尼奥知道枪与圆筒的距离以及圆筒转动的速度,于是他计算出声音在空气中的传播速度为750英里每小时,与今天物理学家普遍认同的声速十分接近.