Bowel movement in an open area by day:[1] When having a bowel movement in an open area by day[2] [such as in a field[3] or in a valley[4]] one must distance himself to the point that the area of his flesh which he uncovers in order to relieve himself [both in the back and in the front[5]] is not visible to others. [It is not necessary for one to distance himself to the point that he is not visible at all, and thus even if he can be seen from a distance it is valid so long as his flesh cannot be seen.[6]] Likewise one is not required to distance himself to the point he cannot be heard. Thus if there is a wall blocking one from being seen, he may relieve himself next to the wall even though there are people on the other side of the wall which can hear him.[7]
[1] Basra 3:3; Kama 3:12; Michaber 3:8
[2] See Basra 3:4
[3] Basra 3:3
[4] Kama 3:12
[5] Basra 3:3
[6] Basra 3:3; Ben Ish Chaiy Vayeitzei 7
[7] Basra ibid; Kama ibid; Olas Tamid 3:10; Ben Ish Chaiy Vayeitzei 7; Unlike Levush [Shaareiy Teshuvah 3:8]
The reason: As there is no prohibition at all of the modesty laws in having people hear him release gas and excrement. [Kama; Basra ibid] (Although this is embarrassing and humiliating for majority of people, nevertheless, if one does not mind, he may do so. Similarly in the times of the Sages of the Talmud they were not bothered by this. See chapter 103:2; Terumos Hadeshen 16.) [Basra ibid; parentheses in original]