For a WLAN design that supports services like internet, email, voice, and database access, a signal strength of
-67 dBm is considered good for voice and streaming services. A 25-dB SNR (Signal-to-Noise Ratio) is also desirable for high-quality voice and video applications, and a maximum of 1 percent packet loss is acceptable to ensure reliable connectivity and service quality.
https://www.cisco.com/c/en/us/support/docs/wireless/5500-series-wireless-controllers/116057site-survey-guideli