My new condenser unit is positioned just outside my bedroom window, and it vibrates quite loudly whenever it's in operation. The bedroom has a door with glass windows that leads to the outside. The noise is keeping me up at night. The setup involves a tall condenser placed on a plastic base over a bed of large pebbles.

Here's a photo of the current setup:

In an attempt to address this problem, I followed a suggestion from reddit and added rubber pads near the screws for the condenser unit; the rubber pads are not shown in the photo but they are essentially just a 1 inch x 1 inch piece of rubber around the screws. While it did help reduce the vibrations to some extent, the noise is still quite noticeable.

I also asked the installer about anti-vibration pads, but unfortunately, they aren't available from the supplier I got the HVAC system from.

Someone recommended considering a riser as a solution, which would involve an additional cost of $850.

Is going for the riser a good idea?

Here's a photo of the riser I'm considering:

Furthermore, I suspect that the bed of pebbles the condenser unit is resting on might be contributing significantly to the vibration noise. So, should I consider replacing the pebbles with something else? If yes, what material would you recommend that could help dampen the vibrations effectively?

TL;DR: New HVAC condenser setup is causing noisy vibrations outside my bedroom window. Added rubber pads but didn't solve the issue completely. Considering a pricey riser option and wondering if it's worth it. Also, thinking about replacing the pebbles under the condenser and seeking suggestions for suitable materials.