I do believe that yelling could be a form of abuse - since issues could most likely be resolved if following the guidelines/examples below. Yelling will only be one-sided temporarily, then before you know it, the kids are older and will respond to you through yelling. Then unfortunately, when two parties are yelling at each other, often times some irreversible things may be stated. This could cause resentment, feelings hurt, damaged relationships, etc... I believe there is a better alternative below...
This is a great question to bring up, since I believe many others share the same.
Personally, I don't yell at my kids at all. I don't spank them either.
However, I have the utmost respect from my kids and I'll tell you why in short...
I'm not an expert, but I have raised 4 children over the years.
What I do is a systematic approach to parenting. I've created specific guidelines for the kids over the years and they understand that if they fall outside those set family rules, there's a relative and definite punishment - regardless. There is no 'but what if....' or 'she started it first....', 'i promise i won't do it again...', etc. The rules my wife and I have set are not flexible, we're very firm and consistent on these set rules. There's no question when they are broken...a penalty must be applied immediately, not at a later time or date - since this will distance the poor behavior with the punishment.
For example - a typical scenario... A mom and/or dad is tired from a very long day at work, but takes his 2 children shopping & tells them that they can have an ice cream after shopping is done. However, the 2 children begin fighting with each other and the parent states - "I've told you before and I will not tell you again, if you continue to fight, NO Ice Cream!!" Five minutes later, the kids are again fighting and both begin to cry. The parent then states I've already told you to both stop!! If I hear Just ONE more from you - we're leaving the store NOW!! Is that understood!!!?? Both kids agree.... yet, another fight breaks out, the parent becomes frustrated, buys them ice cream to make them 'happy' and with all that yelling - there's only built up frustration, the parent is questioning their parenting ability, the parent just wants the kids quiet and will deal with things later - the parent is too tired from working a full day and only wants peace and quiet.
The 2nd scenario, the parent doesn't yell at all. There's no need to, because the children realize that if the parent calmly states - "Are you both listening to me very carefully", as a way to gain the childrens attention and calm them down, then the parent looks at them both in the eye and holds there hands. "If you both don't behave yourselves, i will leave the groceries here, nobody will get ice cream and we're going straight home, then you will both do twice as much homework (or other positive punishment) with no TV or electronics for 2 full days." The kids understand that their parent means business and doesn't need to 'yell' in order to get their attention. The kids KNOW they will be disciplined accordingly.
I honestly believe that speaking and treating a child in a firm, yet positive and respectful manner will help them maintain their composure in challenging times as well. This is what they're learning from their parents that they love dearly.
If a child witnesses a parent screaming at them at the top of their lungs, guess whats going to happen when that child is now an 18 year old adult? Most likely they will scream BACK at their parents, because that's what they've come to understand.
There are many parents that flip/flop - However, if you "walk softly and stay consistent in your actions/words", that's most likely all you'll need - if you start early enough and on the same page with your wife/husband and siblings.