speech_recognition.UnknownValueError - Can someone explain this error to me

I wasn't very sure on what to title this question so I'm sorry if it's not understandable. This project that I've been working on is a Jarvis-related project (Python) recently and this is my error

Traceback (most recent call last):
File "C:\Users\Admin\Rohan_Python\Virtual Assistant.py", line 13, in <module>
text = recog.recognize_google(sound)
File "D:\Rohan_Python\lib\site-packages\speech_recognition\__init__.py", line 858, in 
recognize_google
if not isinstance(actual_result, dict) or len(actual_result.get("alternative", [])) == 0: raise 
UnknownValueError()
speech_recognition.UnknownValueError

My code...

             import pyttsx3 as py
             import speech_recognition as sr
             # initializing speech_recognition
             engine = py.init()
             engine.say("Hey there! I'm Trevor. A virtual assistant for 
             programmers.")
             engine.runAndWait()
             recog = sr.Recognizer()
             with sr.Microphone() as Sound_source:
             recog.energy_threshold = 10000
             recog.adjust_for_ambient_noise(Sound_source, 1.2)
             print("Listening...")
             sound = recog.listen(Sound_source)
             text = recog.recognize_google(sound)
             print(text)

I think this might be a simple error but could someone explain what the error means and what my error is? Also do give me the solution. Please and Thanks!

Solution

Recognition failed. You should catch that error:

try:
    text = recog.recognize_google(sound)
    print(text)
except sr.UnknownValueError:
    print("Could not understand")