Can You Pray Sunnah Out Loud?
Question

Are these prayers done with the recitation out loud or quietly: the optional prayer of Maghrib, the third Rak`ah of Witr prayer when it is done like Maghrib [three consecutive Rak`ahs], Qiyam Al-Layl [voluntary prayers at night], Sunnah of Fajr, and Duha prayer?
Praise be to Allah.Can you pray Sunnah prayer out loud?
The scholars (may Allah have mercy on them) stated that what is prescribed is for the worshipper to recite quietly in optional prayers offered during the day, and when praying at night, he has the choice between reciting out loud or quietly, but reciting out loud is better.
In Kashshaf Al-Qina` (1/441), it says that what is meant by day here is sunrise, not the break of dawn, so the regular Sunnah prayer of Fajr is a prayer that is offered at night.
Based on that, the worshipper should recite quietly in Duha prayer, because it is a prayer that is offered during the day.
With regard to the optional prayer of Maghrib , the third Rak`ah or Witr, Qiyam Al-Layl and the Sunnah of Fajr , the worshipper has the choice between reciting out loud or quietly, although reciting out loud is better, unless reciting quietly helps him to focus more, or he has people with him who will be disturbed by his reciting out loud, such as one who sleeping or one who is sick, and the like.
Shaykh `Abd Al-`Aziz ibn Baz (may Allah have mercy on him) said:
“The Sunnah in prayers at night is to recite out loud, whether the worshipper is praying on his own or has someone else with him. If his wife or other women are praying with him , then they should pray behind him, even if there is only one woman. If he is praying on his own, then he has the choice between reciting out loud or quietly, and what is prescribed is for him to do that which help him focus more. `Aishah (may Allah be pleased with her) was asked about that and she said: The Prophet (blessings and peace of Allah be upon him) would sometimes recite out loud in his night prayers and sometimes he would recite quietly. It is proven from him (blessings and peace of Allah be upon him), in the Hadith of Hudhayfah (may Allah be pleased with him) and others, that he (blessings and peace of Allah be upon him) used to recite out loud in the night prayers; he would pause at a verse that spoke of mercy and ask for mercy, and he would pause at a verse that mentioned punishment and seek refuge with Allah from that, and he would pause at a verse that mentioned glorification of Allah and glorify Him, meaning when reciting verses that mention the divine names and attributes, so he would glorify Allah. Allah, may He be glorified and exalted, says (interpretation of the meaning): {There has certainly been for you in the Messenger of Allah an excellent pattern [example.]} [Al-Ahzab 33:21] And the Prophet (blessings and peace of Allah be upon him) said: “Pray as you have seen me praying.” (Narrated by Al-Bukhari in his Sahih)
These Hadiths indicate that reciting out loud in the night prayers is better, and that is because it helps the heart to focus more and is more beneficial to those who are listening, unless there are people around him who are sick or sleeping, or are praying or reading Quran, in which case it is better for him to lower his voice so that he will not distract other worshippers and readers, or wake up those who are sleeping, or disturb those who are sick.
If he recites quietly in some of the night prayers when he is alone, there is nothing wrong with that, because of the hadith of `Aishah mentioned above, and because that may help him to focus more and may be easier for him sometimes.” (Majmu` Fatawa Ash-Shaykh Ibn Baz, 11/124-125)
The Shaykh (may Allah have mercy on him) also said:
“If a person is praying by himself, it is prescribed for him to do that which will help him to focus more, of reciting out loud or quietly, if he is offering a optional prayer at night and his reciting out loud will not disturb anyone. But if there are people around him who may be disturbed by his reciting out loud, such as other worshippers, people who are reading the Quran or people who are sleeping, it is prescribed for him to keep his voice low.
But with regard to prayers offered during the day, such as Duha prayer , regular Sunnah prayers, Dhuhr and `Asr, the Sunnah is to recite quietly in these prayers.” (Majmu` Fatawa Ash-Shaykh Ibn Baz, 11/126-127)
Can you pray Witr with three Rak`ahs like Maghrib? 
With regard to the questioner mentioning the third Rak`ah of Witr prayer when it is done like Maghrib [three consecutive Rak`ahs], the Prophet (blessings and peace of Allah be upon him) forbade praying Witr in the same manner as Maghrib, and he (blessings and peace of Allah be upon him) said: “Do not pray Witr with three Rak`ahs, making it like Maghrib.” (Narrated by Al-Hakim, 1/304; Al-Bayhaqi, 3/31; Ad-Daraqutni, p. 172) Al-Hafidh Ibn Hajar said in Fat-h Al-Bari (4/301): Its chain of narration is authentic according to the conditions of the two Shaykhs; Al-Bukhari and Muslim.
How the Prophet offered Witr prayer?
It is narrated in an authentic report from the Prophet (blessings and peace of Allah be upon him) that he prayed Witr with three Rak`ahs in two ways:

A prayer of three Rak`ahs with two Tashahhuds and two Salams, so he prayed two Rak`ahs then said the Salam, then he prayed one Rak`ah and said the Salam.

It was narrated that Ibn `Umar (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) used to separate Ash-Shaf` [the even, the first two Rak`ahs of Witr] and Al-witr [the odd, the last Rak`ah of Witr] with a Taslim [saying Salam] that he made us hear. (Narrated by Ibn Hibban, 2435) Al-Hafidh Ibn Hajar said in Fat-h Al-Bari (2/482): “Its chain of narration is strong.”

He would pray the three Rak`ahs with one Tashahhud and two Taslims.

It was narrated that `Aishah (may Allah be pleased with her) said: The Messenger of Allah (blessings and peace of Allah be upon him) used to pray Witr with three Rak`ahs, only sitting [for Tashahhud] in the last of them. (Narrated by Al-Bayhaqi, 4581) This Hadith was classed as authentic by Al-Hakim, and Adh-Dhahabi agreed with him. (Al-Mustadrak, 1/304. Classed as authentic by An-Nawawi in Al-Majmu`, 4/7)
Shaykh Al-Albani (may Allah have mercy on him) said:
“With regard to praying five or three, sitting between each two Rak`ahs without saying the Taslim, we do not find that to be proven from the Prophet (blessings and peace of Allah be upon him). The basic principle is that it is permissible, but because the Prophet (blessings and peace of Allah be upon him) forbade praying Witr with three Rak`ahs, and explained that by saying, “Do not pray Witr with three Rak`ahs, making it like Maghrib,” in that case the one who prays Witr with three Rak`ahs must avoid making it resemble Maghrib, which may be done in two ways:
The first is by saying the Taslim between Ash-shaf` [the even, the first two Rak`ahs of Witr] and Al-witr [the odd, the last Rak`ah of Witr], which is the stronger view and is preferable; and the second is by not sitting [for Tashahhud] between the first two Rak`ahs and the last Rak`ah. And Allah knows best.” (Qiyam Ramadan, p. 22)
And Allah knows best.