Do you think God hears every prayer I pray? Is He busy sometimes answering someone else? Why does the Bible say in some verses "God heard their shout?" Is that just the way it was written? I could find the verses, but I'm sure you remember.
"Now this is the confidence that we have in Him, that if we ask anything according to His will, He hears us. And if we know that He hears us, whatever we ask, we know that we have the petitions that we have asked of Him" (I John 5:14-15).
The key to this confidence is not how many prayers are said, or how loudly they are said, but whether what is being asked is compatible with God's desires. God will not compromise His nature, He won't do things that are wrong.
Thus when people are sinning and think that they have God's ear, they are fooling themselves. "Behold, the LORD'S hand is not shortened, That it cannot save; nor His ear heavy, that it cannot hear. But your iniquities have separated you from your God; and your sins have hidden His face from you, so that He will not hear" (Isaiah 59:1-2). It isn't logical to think that God listens to sinner. "Offer to God thanksgiving, and pay your vows to the Most High. "Call upon Me in the day of trouble; I will deliver you, and you shall glorify Me." But to the wicked God says: "What right have you to declare My statutes, or take My covenant in your mouth, seeing you hate instruction and cast My words behind you?"" (Psalms 50:14-17).
I checked. While there are verses to encourage the Israelites to express their feelings of joy, there isn't one that says God heard their shouts. There are verses that talk about God hearing the Israelites' cries. "And the LORD said: "I have surely seen the oppression of My people who are in Egypt, and have heard their cry because of their taskmasters, for I know their sorrows"" (Exodus 3:7). God knows of our problems and takes note of them. "Then we cried out to the LORD God of our fathers, and the LORD heard our voice and looked on our affliction and our labor and our oppression" (Deuteronomy 26:7; see also Exodus 2:23-25). God doesn't need volume to hear His children. He merely wants their hearts. "And when you pray, you shall not be like the hypocrites. For they love to pray standing in the synagogues and on the corners of the streets, that they may be seen by men. Assuredly, I say to you, they have their reward. But you, when you pray, go into your room, and when you have shut your door, pray to your Father who is in the secret place; and your Father who sees in secret will reward you openly" (Matthew 6:5-6).
But one thing you need to remember, just because you don't get an instant answer it doesn't mean God hasn't heard. Often we are not patient for the best answer, we want it now! There is an old but interesting book called Heidi. It isn't directly a religious book, but it makes several good points. One is that often we don't get instant answers to our prayers because the best answer comes at a later time when all the right pieces are in the right place. Usually we don't realize it until looking back and seeing that if we had gotten an immediate answer, a lot of good would not have taken place.
I also notice that often people tend to ask God to solve problems as they think it should be answered. More often than not, what I might think is the best answer is really a poor one. There often are better ones and when God gives a person one of the better answers people think their prayer wasn't heard because it wasn't exactly what they had asked for.
Let me illustrate it this way: I need to get to my job. I may ask for a new car, but that probably isn't the best answer because that puts me into debt, which limits what I can do. Perhaps the better answer comes as the city puts in a new bus stop close to my house. Or I might lose my job, forced to move to a new town and find out that I'm close to work now and my expenses are less in this new place. Now at first I might think God isn't listening, but in the end I can see that God not only listened but gave me more than I expected.