AC Compressor making noise

[Fixer]

My outdoor compressor unit is making a buzzing sound.  It appears to be cooling okay though it is an old R22 unit.  I attached a recording made about 3 feet from the unit so you can hear it.  I'm also attaching a photo of the unit itself and the label on the back. I'm new to the house so I don't know what it sounded like when it was new or what the history is on the unit. 

• Is it possible this sound is normal for this kind of unit? 
• If not, can we say anything about what I can expect going forward, like how long it may be before it stops cooling?

[Fixer]

Opps, the audio file is not working so let me try that again.  I attached it here.  Also, as seen on the label the compressor unit is Carrier 24ABR360A360.