If you are deaf or hard of hearing, there are several accessibility features available to you.
A text transcript is a text equivalent of audio information that includes spoken words and non-spoken sounds such as sound effects.
A caption is transcript for the audio track of a video presentation that is synchronized with the video and audio tracks. Captions are generally rendered visually by being superimposed over the video, which benefits people who are deaf and hard-of-hearing, and anyone who cannot hear the audio (e.g., when in a crowded room). Most of NAR's video content includes captions. Learn how to turn captioning on and off in YouTube. (link is external)
Your computer, tablet, or mobile device has volume control features. Each video and audio service has its own additional volume controls. Try adjusting both your device's volume controls and your media players' volume controls to optimize your listening experience.