If your pump units are using Imperial submersible motors they had a rash of problems due to a issue in manufacturing that had something to do with lamination on the armature. This would cause not only a good amount of noise but in some cases a great amount of pulsation which transferred over to the ride quality. It threw a lot of people off because the natural reaction was to look at the pump or muffler being that the elevator would still run a contract speed in the up direction.

We recently replaced a TKE submersible motor with a US Submersible motor on one car in a duplex and it was amazing how much quieter the US motor ran compared to the original TKE motor next to it.

Another option is these guys: www.myicdinc.com (silentknight pumping units) I havn't seen one yet but might be just the thing your looking for when it comes to a noise sensitive building.