p, t, k, θ, s, ∫, h, t∫/ are called

The correct answer is Voiceless consonants.

Key Points

• An easy way to determine whether a consonant is voiced or not is to place a finger on your throat. As you pronounce a letter, feel the vibration of your vocal cords. If you feel a vibration the consonant is a voiced one.
• Some voiced consonants might be produced by blending the two consonants phonetically.
• Consonants is a sound we make which is not a vowel. 
• For example:
  • In bat b and t are consonants.
  • In pen p and n are consonants.
• The English letters B, c, d, f, g, h, j, k, l, m, n, p, q, r, s, t, v, w, x, y, z.
• There are 24 consonants sounds in English divided into 2 types:
  • Voiced sounds - 15 (B, D, G, J, L, M, N, Ng, R, Sz, Th, V, W, Y, and Z)
  • Voiceless sounds - 9 (Ch, F, K, P, S, Sh, T, and Th)