Sometimes when I get out of my car and shut the door I can hear from the inside some type of buzzing noise. It almost sounds like a quiet and muffled version of the horn. It lasts for about 2-3 seconds until it fades out and stops making the noise. Any thoughts on what it could be?

 

i hear the same thing on my 99 si. Not sure what it is but seems normal

 

https://honda-tech.com/zerothread?id=234775