Is it permissible to lower the volume of the Fajr adhan in response to the request of Jews residing near Muslims, who are bothered by its high volume during their sleep, knowing that they do not object to the high volume at other times?

If you are compelled to lower the volume of the loudspeakers, then there is no harm in it. However, if it is possible to keep it as it is, then do not change it, for raising the voice with the Adhan (definition) is a legitimate Islamic requirement and fulfills the purpose of the Adhan, especially for the Fajr prayer, to awaken the Muslims. The Messenger of Allah, peace and blessings be upon him, said: "No jinn, human, or anything hears the extent of the muezzin's voice except that it will bear witness for him on the Day of Resurrection."