| AIR CONDITIONER | HUM |
| AT A LOSS FOR WORDS | HUM |
| ATTILA | HUM |
| BACKGROUND NOISE | HUM |
| BE AT A LOSS FOR WORDS? | HUM |
| BE BUSY, AS A BEE | HUM |
| BE BUSY | HUM |
| BEE ACTIVITY | HUM |
| BEE FOLLOWER | HUM |
| BEE SOUND | HUM |
| BEEHIVE SOUND | HUM |
| BEES MAKE IT | HUM |
| BOMBINATE | HUM |
| BUMBLE | HUM |
| BUSILY EMPLOY | HUM |
| BUSILY WORKING | HUM |
| BUSTLE | HUM |
| BUSY AND ACTIVE | HUM |
| BUZZ | HUM |
| CONTINUOUS SOUND | HUM |
| CROON | HUM |
| DRONE | HUM |
| DRONING SOUND | HUM |
| ENGINE NOISE | HUM |
| ENGINE SOUND | HUM |
| FAN NOISE | HUM |
| FIRE ON ALL CYLINDERS | HUM |
| GO SMOOTHLY | HUM |
| GOOD ENGINE SOUND | HUM |
| HUMMING | HUM |
| INDISTINCT MURMUR | HUM |
| LOW DRONE | HUM |
| LOW MURMUR | HUM |
| LOW SOUND | HUM |
| LOW, DRONING SOUND | HUM |
| MACHINE SOUND | HUM |
| MAKE A LOW CONTINUOUS SOUND | HUM |
| MOAN | HUM |
| MOTOR SOUND | HUM |
| MUTTERING | HUM |
| MUTTER | HUM |
| ODOUR | HUM |
| OPERATE SMOOTHLY | HUM |
| PLAY A KAZOO | HUM |
| PROCEED SMOOTHLY | HUM |
| PURR | HUM |
| REVERBERATE | HUM |
| RHYTHMIC SOUND | HUM |
| RUN NICELY | HUM |
| RUN SMOOTHLY | HUM |
| RUN SMOOTHLY, AS AN ENGINE | HUM |
| RUN WELL | HUM |
| SING LOW | HUM |
| SING WITH MOUTH CLOSED | HUM |
| SING WITH CLOSED MOUTH | HUM |
| SING WITH LIPS CLOSED | HUM |
| SING WITH A CLOSED MOUTH | HUM |
| SING, IN A WAY | HUM |
| SING WITHOUT WORDS | HUM |
| SING WORDLESSLY | HUM |
| SING WITH CLOSED LIPS | HUM |
| SMOOTH ENGINE SOUND | HUM |
| SOUND FROM A FAN | HUM |
| SOUND OF A FAN | HUM |
| SOUND OF BEES | HUM |
| SOUND OF HESITATION | HUM |
| SYMPTOM FOR A CAR MECHANIC | HUM |
| THRUM | HUM |
| UNDERTONE | HUM |
| UNPLEASANT SMELL | HUM |
| USE KAZOOS | HUM |
| VIBRATION SOUND | HUM |
| VIBRATE | HUM |
| WHIR | HUM |
| WHIRR | HUM |
| WHISPERING | HUM |
| WHIZ | HUM |
| WITHOUT WORDS SING | HUM |
| WORK SMOOTHLY | HUM |
| ZOOM | HUM |