Small macOS utility to ensure system is muted when asleep to prevent potential sounds during Power Nap; Addresses reddit issue: https://www.reddit.com/r/apple/comments/8t041u/my_macbook_creeps_me_out_by_starting_to_talk_in/

muteonsleep.swift

//
// MuteOnSleep
// Ensures system is muted when asleep to prevent potential sounds during Power Nap
//
// Install by pasting the following in a terminal prompt:
// curl https://s3.amazonaws.com/muteonsleep-tool/muteonsleep.tar.gz | tar xvz -C /usr/local/bin/; osascript -e 'tell application "System Events" to make login item at end with properties {path:"/usr/local/bin/muteonsleep", hidden:true}'; nohup /usr/local/bin/muteonsleep &
//
// Uninstall with:
// pkill muteonsleep; osascript -e 'tell application "System Events" to delete login item "muteonsleep"'; rm /usr/local/bin/muteonsleep
//

import Foundation
import AppKit

@discardableResult func executeAppleScript(source: String) -> String {
  let process = Process()
  process.launchPath = "/usr/bin/osascript"
  process.arguments = [String(format: "-e %@", source)]
  
  let pipe = Pipe()
  process.standardOutput = pipe
  process.launch()
  
  let data = pipe.fileHandleForReading.readDataToEndOfFile()
  guard let output = String(data: data, encoding: .utf8) else {
    return ""
  }
  
  return output.trimmingCharacters(in: .whitespacesAndNewlines)
}

func isMuted() -> Bool {
  return executeAppleScript(source: "output muted of (get volume settings)") == "true"
}

func mute() {
  executeAppleScript(source: "set volume with output muted")
}

func unmute() {
  executeAppleScript(source: "set volume without output muted")
}

var alreadyMutedBeforeSleep = false

let notificationCenter = NSWorkspace.shared.notificationCenter
notificationCenter.addObserver(forName: NSWorkspace.willSleepNotification,
                               object: nil,
                               queue: nil,
                               using: { _ in
  alreadyMutedBeforeSleep = isMuted()
  if !alreadyMutedBeforeSleep {
    mute()
  }
})

notificationCenter.addObserver(forName: NSWorkspace.didWakeNotification,
                               object: nil,
                               queue: nil,
                               using: { _ in
  if !alreadyMutedBeforeSleep {
    unmute()
  }
})

RunLoop.current.run()