文件浏览框选择指定wav文件并绘制1/3倍频程结果，要求封装成函数或者类Python代码

以下是一个封装成类的Python代码示例，实现选择指定wav文件并绘制1/3倍频程结果：

import wave
import numpy as np
import matplotlib.pyplot as plt
from tkinter import filedialog
from tkinter import *

class WavPlotter:
    def __init__(self):
        self.filename = None
        self.sampling_rate = None
        self.data = None

    def load_file(self):
        root = Tk()
        root.withdraw()
        self.filename = filedialog.askopenfilename(initialdir="./", title="Select a Wav File", filetypes=(("WAV files", "*.wav"),("all files", "*.*")))
        with wave.open(self.filename, 'rb') as wav_file:
            self.sampling_rate = wav_file.getframerate()
            self.data = np.frombuffer(wav_file.readframes(-1), dtype=np.int16)

    def plot_third_octave_spectrum(self):
        if self.filename is None:
            self.load_file()
        freq, fft = self._get_fft()
        third_octave_bands = self._get_third_octave_bands()
        third_octave_fft = self._get_third_octave_fft(fft, freq, third_octave_bands)
        plt.plot(third_octave_bands, third_octave_fft)
        plt.xscale('log')
        plt.xlim([20, self.sampling_rate / 2])
        plt.ylim([0, max(third_octave_fft) * 1.1])
        plt.xlabel('Frequency (Hz)')
        plt.ylabel('Amplitude')
        plt.title('1/3 Octave Spectrum')
        plt.show()

    def _get_fft(self):
        n = len(self.data)
        fft = np.fft.fft(self.data)
        freq = np.fft.fftfreq(n, d=1/self.sampling_rate)
        return freq[:n//2], np.abs(fft[:n//2])

    def _get_third_octave_bands(self):
        center_frequencies = np.array([25, 31.5, 40, 50, 63, 80, 100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150, 4000, 5000, 6300, 8000, 10000, 12500, 16000, 20000])
        lower_frequencies = center_frequencies / np.power(10, 1/6)
        upper_frequencies = center_frequencies * np.power(10, 1/6)
        return (lower_frequencies * upper_frequencies) ** 0.5

    def _get_third_octave_fft(self, fft, freq, third_octave_bands):
        third_octave_fft = []
        for i in range(len(third_octave_bands) - 1):
            lower_index = np.argmin(np.abs(freq - third_octave_bands[i]))
            upper_index = np.argmin(np.abs(freq - third_octave_bands[i+1]))
            third_octave_fft.append(np.mean(fft[lower_index:upper_index]))
        return third_octave_fft

使用示例：

wav_plotter = WavPlotter()
wav_plotter.load_file()
wav_plotter.plot_third_octave_spectrum()

其中 `load_file` 方法用于打开文件选择对话框并加载选择的wav文件，`plot_third_octave_spectrum` 方法用于绘制1/3倍频程结果，内部调用 `_get_fft`、`_get_third_octave_bands` 和 `_get_third_octave_fft` 方法实现频率域处理。