Let’s look at the verses you are referring to. Psalms 55:17 says, “Evening, and morning, and at noon, will I pray, and CRY ALOUD: and he shall hear my voice.” Matthew 6:2 says, “Therefore when thou doest thine alms, do not sound a trumpet before thee, as the hypocrites do in the synagogues and in the streets, THAT THEY MAY HAVE GLORY OF MEN. Verily I say unto you, They have their reward.” Matthew 6:5 says, “And when thou prayest, thou shalt not be as the hypocrites are: for they love to pray standing in the synagogues and in the corners of the streets, THAT THEY MAY BE SEEN OF MEN. Verily I say unto you, They have their reward.” Matthew 6:16 says, “Moreover when ye fast, be not, as the hypocrites, of a sad countenance: for they disfigure their faces, THAT THEY MAY APPEAR UNTO MEN TO FAST. Verily I say unto you, They have their reward.”

In David’s psalm (Psalm 55), in verse 17, he says that he will ‘cry aloud’ to the Lord. The meaning of this phrase is that he will ‘complain and murmur’ to the Lord. He was addressing the distress he was in, the fervency of his prayer, and how his voice would be applicable to his petitions to the Lord. Perhaps he might speak softly at times in his prayers, perhaps he may raise his voice as he implores the Lord for His needs. David’s words to not seem to imply that these are public prayers, but private ones.

In Matthew 6:2, 5, and 16, we can recognize that the problems with these hypocrites was that they were simply longing for attention. They desired the glory of men. They loved to be seen of men. They fasted so that others would notice them. In each case we read, “They have their reward.” Matthew 23:5 even tells us that, “all their works they do for to be seen of men…” These hypocrites were not ‘crying aloud’ to the Lord. They were making noises and gathering attention so that they might be exalted above other men. We read in Mark 7:6, “This people with the lips doth honour Me, and their heart is far from Me.” The Lord knows the intent and condition of the heart. If we call upon His name only to be heard of men, the Lord knows that and will react appropriately. To call upon Him loudly is no sin, to call upon Him loudly so that others will see us and consider us to be spiritual is grievous sin. It is hypocrisy. (296.6)