Xiaomei classmate information consultation

According to the imaging characteristics of flat mirror, we can know that the image is the same size as the object, and the distance between the image and the object is the same, just like a virtual image;

So the distance from the image to the plane mirror is also 1.5m, and the distance from the image to her is1.5m+1.5m = 3m;

Timbre reflects the quality and characteristics of sound. When we hear an acquaintance talking on the phone, we can tell who the other person is, and we can tell by the timbre of the voice made by the other person, so Xiaomei can tell that it is Xiaoling according to the timbre of the voice.

So, the answer is: virtual; 3; Timbre.