If you want to use it only for specific apps (like WhatsApp), go into the and select the Whistle sound from there so it doesn't clash with your general system alerts.

If you are looking to get this classic sound back on your modern device for free, here is everything you need to know. Why It’s Iconic

Since this is a legacy tone, it isn't always pre-installed on the newest S24 or Z Fold models. Here are the easiest ways to download it:

The whistle sound was designed to mimic nature, fitting Samsung’s "inspired by nature" branding at the time. It became so ubiquitous that even today, hearing it immediately signals a "Samsung message" to many people. How to Get It for Free

Sites like NotificationSounds.com or Mobiles24 host the original .mp3 or .ogg files.