All praise is due to Allah, and may peace and blessings be upon the Messenger of Allah.
First: The legitimacy of obtaining the trace of the person who caused the evil eye
The Prophetic Sunnah establishes the permissibility of obtaining the trace of the person who caused the evil eye and washing with it as a treatment for the afflicted person.
Abu Umamah ibn Sahl ibn Hunayf narrated from his father (may Allah be pleased with them both) that the Prophet ﷺ instructed Amir ibn Rabi'ah to perform ritual washing for Sahl ibn Hunayf after he had afflicted him with the evil eye. He washed his face, hands, elbows, knees, feet, and the inside of his lower garment in a vessel. Then that water was poured over Sahl, and he got up and went among the people without suffering any harm. Narrated by Ahmad and Ibn Majah.
Second: How to obtain the trace of the person who caused the evil eye
The trace should be obtained from something that has directly come into contact with the person's body, such as the water remaining from their ablution or ritual washing, something from their clothing that touches their body, or the remains of their food and drink that their saliva has touched. These traces are then placed in water, which can be used for drinking or washing.
Third: The ruling on obtaining the trace through sound vibrations over the phone
Obtaining the trace of the person who caused the evil eye through this method is not valid. Sound vibrations transmitted through a phone do not transfer the person's physical substance or saliva into the water. Therefore, they are not considered a trace of that person, and there is no evidence that this method is a valid means of treatment.
Conclusion: It is permissible to obtain the trace of the person who caused the evil eye from something that directly touched their body or came into contact with their saliva. However, placing a phone next to water while that person is speaking does not constitute obtaining their trace, and this method should not be relied upon as a treatment.
And Allah knows best.