A more realistic sound of the vehicle.

Hello! I want to change the sound of the car more realistic.

The current effect is a little boring (sound pitch to be changed with the speed).I searched the Internet solution but have not found anything interesting. Can I use this script can create the effect of shifting? If so, how?

Example sound effect: https://youtu.be/TKNjFv4DRF0?t=48s C# script

 using UnityEngine;
 using System.Collections;
 
 public class RearWheelDriveXp : MonoBehaviour
 {
 
     private WheelCollider[] wheels;
 
     public float maxAngle = 30;
     public float maxTorque = 300;
 
     public float topSpeed = 100; // km per hour
     public float currentSpeed = 0;
     private float pitch = 4f;
 
     public Transform visualCar;
 
     public GameObject CarEngine;
 
     public float Brakes;
     public float BrakesForce;
 
     // here we find all the WheelColliders down in the hierarchy
     public void Start()
     {
         wheels = GetComponentsInChildren<WheelCollider>();
         GetComponent<Rigidbody>().centerOfMass = visualCar.localPosition;
 
     }
 
     // this is a really simple approach to updating wheels
     // here we simulate a rear wheel drive car and assume that the car is perfectly symmetric at local zero
     // this helps us to figure our which wheels are front ones and which are rear
     public void Update()
     {
 
 
         float angle = maxAngle * Input.GetAxis("Horizontal");
         float torque = maxTorque * Input.GetAxis("Vertical");
 
         Brakes = 0;
         if (Input.GetKey(KeyCode.Space) == true)
         {
             Brakes = BrakesForce;
         }
         foreach (WheelCollider WC in wheels)
         {
             WC.brakeTorque = Brakes;
         }
 
         foreach (WheelCollider wheel in wheels)
         {
             // a simple car where front wheels steer while rear ones drive
             if (wheel.transform.localPosition.z > 0)
                 wheel.steerAngle = angle;
 
             if (wheel.transform.localPosition.z < 0)
                 wheel.motorTorque = torque;
 
             // update visual wheels if any
             {
                 Quaternion q;
                 Vector3 p;
                 wheel.GetWorldPose(out p, out q);
 
                 // assume that the only child of the wheelcollider is the wheel shape
                 Transform shapeTransform = visualCar.FindChild(wheel.name);
                 shapeTransform.position = p;
                 shapeTransform.rotation = q;
             }
 
         }
 
 
 
         // CURRENTSPEED
         currentSpeed = (Mathf.Round(GetComponent<Rigidbody>().velocity.magnitude));
 
         // ENGINE SOUND
         pitch = currentSpeed / topSpeed;
         CarEngine.GetComponent<AudioSource>().pitch = pitch + 0.5f;
   
 
     }
 
     public void FixedUpdate()
     {
         if (currentSpeed > topSpeed)
         {
             GetComponent<Rigidbody>().velocity = GetComponent<Rigidbody>().velocity.normalized * topSpeed;
         }
 
         GetComponent<Rigidbody>().velocity = Vector3.ClampMagnitude(GetComponent<Rigidbody>().velocity, topSpeed);
     }
 }