STAMFORD — A $23,000 gift from a local nonprofit is being used to purchase roomy cat cages for the city’s animal shelter. In addition to the cages, H/3 is paying for soundproofing that will prevent noise in the dog kennel from reaching other parts of the building, and for new speakers that will play soothing classical music in the cat room. The animal control center relies heavily on help and donations from volunteer organizations like STARelief, which provides assistance to pet owners who find themselves unable to afford caring for their animals.