I read what fredrik is asking for but also agreed with Vin. mIRC is not a bad client if one knows how to use it i've been using it since 2000 so its quiet friendly client i've ever used.
mIRC can be configured to not beep on notice in Options > Sounds > On Event Play Sound: Notice > No Sound. The number and delay of beeps can also be adjusted in this spot. The client isn't poor or defenseless against being configured to suit the needs of the end user, which in this case sounds like just turning off some beeps.
Furthermore regarding channel notices even i have suggestion as a member of help channels we receive complaints regarding channel notice flood etc. so i have a suggestion here if we can have a channel mode where only channel notices can be blocked except channel option verbose notices.