Can my neighbor in the adjacent townhouse play his stereo loud enough that I can hear and feel the music through the walls?

I live in a townhouse in Seattle and have been bothered by repeated episodes of loud music emanating from my neighbor's adjacent townhouse. I have politely requested in writing and in person that he lower the volume on several occasions. Despite his promise to control the noise and to keep it quiet by 10 pm weekdays and 11pm weekends, the problem has persisted. When standing outside his front door, however, it is not loud. So, the noise only affects my neighboring townhouse from the inside. This is decreasing the quality of my life and I'm not sure what legal remedies exist.