Sample-accurate volume ramp (Unity)

using UnityEngine;
using System.Collections;

public class VolRamp : MonoBehaviour {

    public float rampTime = 1f; // in seconds

    private float _volume = 0f;
    private float _volumeDelta;


    void Awake () {
        AudioSource audioSource = GetComponent<AudioSource>();
        _volumeDelta = 1f / ((float)audioSource.clip.frequency * rampTime);
    }

    void OnAudioFilterRead (float[] data, int numChannels) {
        for (int i = 0; i < data.Length; ++i) {
            if (_volume < 1f) {
                _volume += _volumeDelta;
            }

            data[i] *= _volume;
        }
    }

}