Blynk Notification from system is a Legacy command. It doesn’t work with Blynk IoT and needs to be removed from your sketch.

The syntax for Blynk.logEvent() is…



Blynk.logEvent("event_code", "optional custom message")

According to your screenshots your event code is “sound” so your command should look like this…



Blynk.logEvent("sound", "additional message regarding sound level")

However, there is a limit of 100 events per 24 hour period, and your code will easily exceed this if it detects a high level of sound for 100 iterations of your void loop.

You should read this for more info on how to avoid this issue…

Also, you shouldn’t have this code in your void loop, and you should use BlynkTimer instead of the blocking delay() commands that you are currently using.
Read this for more info…