This is a macOS version of the HotPaw Morse Decoder app for iPhone and iPad.
The HotPaw Morse Code Decoder can decode the sounds of Morse Code characters, and transcribe the results into text. 
Both an audio spectrum graph and a tone amplitude graph are displayed to assist with setting a narrow band audio filter.  The audio filter can be set for tone frequencies in the range of 400 to 1600 Hz.  
Other user configurable settings include the WPM dot/dash speed used for Morse code detection, a noise threshold level, and whether Farnsworth timing is to be used for detecting spaces between characters. The Morse code WPM (words per minute) detection speed is automatically adaptive from about 8 to 40 WPM, and can be locked to the current estimated WPM dot speed (WPM lock icon locked). There is a High Speed WPM Mode which may work better for code speeds in the range of 40 to 80 WPM.
The quality of Morse code decoding depends on the signal level, signal-to-noise ratio, stability of the frequency and WPM speed, keying "fist" quality, and whether you have configured the app properly for the signal. It may take several initial preceding Morse Code characters containing both dots and dashes before the WPM speed estimation starts to lock on to the actual WPM. Background sounds and signal fading can interfere with detection and decoding. The built-in microphone on some MacBook models has been reported not to work optimally, due to the pick up of fan noise and/or room or table reverberations of the pure Morse code tones. In those situations, an external microphone or line-in may be necessary to allow a good decode of CW sounds. Please use the manual settings if automatic decoding does not adjust to the frequency, WPM or background noise threshold level. Please see the help file on the HotPaw website for suggestions on the proper settings to detect Morse code signals.