In the Lorentz transformation, light is chosen as the observation medium to derive the coordinate relationship for spacetime conversion, which is then applied in the theory of special relativity. However, this approach overlooks the impact of the characteristics of the selected observation medium on spacetime conversion, leading to limitations in the understanding of spacetime effects. This paper proposes a new Extended Lorentz Transformation theory and methodology. The analysis results lead to an important conclusion: spacetime effects are essentially subjective measurement errors caused by the observation method and are independent of the reference frame and the motion state of the object. The speed of the observation medium is the fundamental cause of measurement errors. The higher the speed, the smaller the error. When the speed is infinite, the spacetime effects vanish, and the measurement error becomes zero. Acoustic waves are used as the observation medium for verification. The results show that even when the object's motion speed is relatively low, significant space-time effects can still occur, leading to substantial measurement errors. Compared with light under the same conditions, there are significant differences in spacetime effects, indicating that the light observation medium is merely a special case of human subjective choice for observing the motion of objects, and the observation results do not have universal applicability. The conclusion regarding spacetime effects in Einstein's special relativity does not hold. To further expand the scope of applicability of relativity, this paper derives the formula for calculating space-time effects in non-uniformly speed reference frames.