hum
剑桥词典
hum verb (MAKE A NOISE)
[ 不及物动词：后面不接宾语的动词 ]to make a continuous low sound
发出连续低沉的声音，嗡嗡作响
The computers were humming in the background . 计算机在背景中嗡嗡作响。
What's that strange humming sound ? 那种奇怪的嗡嗡声是什么？
[ 不及物动词：后面不接宾语的动词 or 及物动词：后面接宾语的动词 ]
to sing without opening your mouth
哼（曲子）
She hummed to herself as she walked to school . 她在上学的路上边走边哼曲子。
I've forgotten how that song goes - could you hum it for me? 我忘了那个调子怎么唱了——你能给我哼一下吗？
[ 不及物动词：后面不接宾语的动词 ] informal
to be busy and full of activity , excitement , sounds , or voices
忙乱，忙碌；嘈杂
The bar was really humming last night . 昨晚酒吧里一片乱哄哄的。