How to import wav file trough script from Project folder?

Why do you want to make this?

Are you using unity's implementation of microphone recording? https://docs.unity3d.com/ScriptReference/$$anonymous$$icrophone.html

If you do, function $$anonymous$$icrophone.Start return AudioClip object which you can use with an AudioSource

Here is a script that I made hopefully it helps out

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 using System.IO;
 
 public class AudioAccessor: $$anonymous$$onoBehaviour 
 {
     //In this case I never looked for the game folder ins$$anonymous$$d i checked for the audio files in "my documents"
     private string GamePath;
     private DirectoryInfo GameDirectory;
 
     //Audio info
     private DirectoryInfo AudioDirectory;
     private string AudioPath;
 
     private FileInfo[] AudioFilesFound;
     private AudioClip clip;
     public List<AudioClip> LoadedAudioWeapons = new List<AudioClip>();
 
     void Start()
     {
         CheckFoldersAndLoad$$anonymous$$odObjects();
     }
     
     public void CheckFoldersAndLoad$$anonymous$$odObjects () 
     {
         if(File.Exists(System.Environment.SpecialFolder.$$anonymous$$yDocuments + "\\TheGamesName") == false)//if there was nothing found in my documents then create them
         {
             CreateFolder();
         }
         else //Otherwise if the stuff exists just the the path
         {
             GameDirectory = System.IO.Directory.CreateDirectory(System.Environment.GetFolderPath(System.Environment.SpecialFolder.$$anonymous$$yDocuments) + "\\TheGamesName");
             GamePath = GameDirectory.FullName.ToString();
         }
 
         //Load all objects from folders here
         GetAudioFromFolder();
     }
 
     //Creation of files
     private void CreateFolder()
     {
         GameDirectory   = System.IO.Directory.CreateDirectory(System.Environment.GetFolderPath(System.Environment.SpecialFolder.$$anonymous$$yDocuments) + "\\TheGamesName");
         GamePath        = GameDirectory.FullName.ToString();
     }
 
     private void GetAudioFromFolder()
     {
         AudioFilesFound = GameDirectory.GetFiles("*.ogg*");//Gets all files with the format ".ogg"
 
         for (int k = 0; k < AudioFilesFound.Length; k++)
         {
             StartCoroutine(LoadAudioWeapons(AudioFilesFound[k].ToString()));
         }
     }
 
     private IEnumerator LoadAudioWeapons(string fileName)
     {
         WWW www = new WWW("File:///" + fileName);
         yield return www;
 
         if(Path.GetExtension(fileName).ToUpper() == ".OGG") 
             clip = www.GetAudioClip(true, false, AudioType.OGGVORBIS);
 
         while (clip.loadState == AudioDataLoadState.Loading)
             yield return www;
 
         clip.name = Path.GetFileName(fileName);
         LoadedAudioWeapons.Add(clip);
     }
 }

It accesses the files from my documents, you might want yo change the file path if you want to access your project folder, i think its Application.dataPath but I'm to lazy to look XD

Another note, I'm not to sure if you can import .wav so you just going to have to double check as I originally wanted to import .mp3 but unity wouldn't allow it.