Thought to have originated from the San Fernando Valley in Southern California and most commonly attributed to "Valley girls", a socio-economically stereotyped class of women referring to upper-middle class girls characterized as ditzy or airheaded, Valleyspeak is an American English sociolect.
The most defining feature of Valleyspeak is the high rising terminal intonation pattern or "uptalk" - statements have rising intonation, causing normal declarative language to appear interrogative.
Another feature often associated is the glottal fry or vocal fry. The low, creaky sound is the acoustic result of staccato, irregular vibrations of the vocal cords. Typically noted at the end of sentences, it is observed in conjunction with a low pitch and suboptimal airflow.
BUT WHY DOES IT MATTER?
There are a few polarizing views on the topic. A study by Anderson, Klofstad, Mayew & Venkatachalam suggests,
"Young adult female voices exhibiting vocal fry are perceived as less competent, less educated, less trustworthy, less attractive, and less hirable. The negative perceptions of women who use vocal fry are stronger when the listener is also a woman. Collectively, these results suggest young American women should avoid vocal fry in order to maximize labor market perceptions, particularly when being interviewed by another woman."
A VICE reporter brought his girlfriend to a SLP to specifically address glottal fry. Although millennials appears to be more tolerant of the vocal technique and Yuasa (2010) suggests glottal fry is perceived as "hesitant, nonaggressive, and informal but also educated, urban-oriented, and upwardly mobile", I think it is important to be aware of and know when it is appropriate. In my subjective opinion, I am skeptical that glottal fry globally holds the connotation of educated, urban-oriented and upwardly mobile and instead may reflect a geography-specific opinion held in California where the study was completed.
In the VICE article, it is summed up nice.
"There are a lot of industries like health care, law and education where that vocal pattern is frowned upon and could be perceived as a lack of knowledge, which of course is complete bullshit. But it's the perception. It's not reality, but we need to be careful of that."
SO WHAT CAN YOU DO?
If you have set off on a quest to rid yourself of the uptalk and creaky voice. Here are a few guidelines for you.
1. Record yourself and listen.
If you don't even know if you do it, how can you address the problem? Record a conversation over dinner or a phone call. Pay close attention to the end of your thoughts and sentences.
2. Practice speaking out loud
First, simple words (e.g. Hi, Bye), then simple phrases (e.g. Good morning, Happy birthday), then simple sentences (e.g. I hope you have a great day), then longer sentences/paragraphs/etc. Listen carefully to notice any uptalk or glottal fry.
You are not asking questions, so there should not be any rising intonation at the end of the sentence. Variation in your intonation is fine throughout the sentence - you avoid being monotonous or "boring", but avoid rising at the end.
3. Breath support
Many times, glottal fry happens at the end of a sentence because you don't have the breath support to vibrate the vocal cords adequately. Get used to that feeling so you know when you are running out of breath. Simple solutions include taking a deeper breath next time or stopping and taking another breath.
I think it's important to recognize that not every word that comes out of your mouth is glottal fry or uptalk. Unless you have a medical condition that affects your voice production, you can and do speak in part without the glottal fry or uptalk - so it's not impossible to stop. It will just take time, patience, and practice...like all good things in life.