A computer-implemented method for estimating noise performance of a rolling tire, comprising: a tire model defining process in which a tire model, which is a finite element model of the tire and has a tread and grooves therein, is defined in a computer, a rough road surface model defining process in which a rough road surface model, which is a finite element model of a rough road surface, is defined in the computer, a rolling simulation process in which calculations of the tire model, which contacts with the rough road surface model and is rolling thereon, are performed, a coordinates data obtaining process in which coordinates data on node points appearing in the outer surface of the rolling tire model which data are obtained through the rolling simulation process, are stored in the computer as time-series coordinates data, a sound field defining process in which a smooth road surface model, which is a finite element model of a smooth road surface, a tire outer surface model, which is the outer surface of the tire model defined by said coordinates data obtained, and a sound field in which airflow is possible and which encompasses at least a ground contacting part of the tire outer surface model and the corresponding part of the smooth road surface model, are defined in the computer, a noise simulation process in which physical quantities of the sound field are computed, rolling the tire outer surface model by the use of the time-series coordinates data, wherein the method further comprises: a process in which at least said ground contacting part of the tire outer surface model is separated from the smooth road surface model by small distance so that a gap is formed between the tire outer surface model and the smooth road surface model, wherein said sound field is also defined in the gap. a tire model defining process in which a tire model, which is a finite element model of the tire and has a tread and grooves therein, is defined in a computer, a rough road surface model defining process in which a rough road surface model, which is a finite element model of a rough road surface, is defined in the computer, a rolling simulation process in which calculations of the tire model, which contacts with the rough road surface model and is rolling thereon, are performed, a coordinates data obtaining process in which coordinates data on node points appearing in the outer surface of the rolling tire model which data are obtained through the rolling simulation process, are stored in the computer as time-series coordinates data, a sound field defining process in which a smooth road surface model, which is a finite element model of a smooth road surface, a tire outer surface model, which is the outer surface of the tire model defined by said coordinates data obtained, and a sound field in which airflow is possible and which encompasses at least a ground contacting part of the tire outer surface model and the corresponding part of the smooth road surface model, are defined in the computer, a noise simulation process in which physical quantities of the sound field are computed, rolling the tire outer surface model by the use of the time-series coordinates data, wherein the method further comprises: a process in which at least said ground contacting part of the tire outer surface model is separated from the smooth road surface model by small distance so that a gap is formed between the tire outer surface model and the smooth road surface model, wherein said sound field is also defined in the gap.