Yelled at in stereotypical gibberish

A multiracial group of people were social distancing outside the fence of the home of an East Asian family. One of the parents was celebrating a birthday and the family was gathered in their backyard while friends were arrayed along the fence. A middle-aged masculine person was biking down the sidewalk toward the house and I noticed that they were yelling something at the family/our group. At first I thought it was birthday greetings from a neighbor but as the person biked closer I realized they were shouting Asian-sounding gibberish (i.e. "ching chong" noises) at us. I shouted after them but they were already biking away.