What causes the buzzing noise when the Civic reaches 70 mph?

[EmiliaFitz]

If there is abnormal noise when the car reaches 70 mph, it is likely tire noise. If the noise gets louder as the speed increases, it could be a bad bearing. Below are some relevant information about checking abnormal car noises: Check the valve chamber: If the car hasn't been driven for a while, the engine oil will return to the oil pan, and the valve chamber will have less oil. Due to the lack of oil for sealing and lubrication in the valve chamber, you may hear a hissing sound from the bottom of the car when it is first started. This situation is normal. Check the engine belt: You can try pinching the drive belt with your fingers and then twisting it, but the twist angle should be less than 90 degrees. If the engine belt is too dirty, it can cause abnormal noise. Cleaning it with water or using some lubricant can eliminate the noise. Check the engine mount bolts: Loose engine mount bolts can cause improper installation of the engine support. Check the engine compartment: There may be foreign objects blocking the engine compartment.