Yes, you can, but really the Power, laid in the Sacral Words of Power, will be «muted». If you live not alone, but, for example, with your parents, you can Vibrate quietly. This problem is especially acute for minor children living with Christian parents. It is a problem and, of course, it is necessary to provide one's own personal space for Spiritual Working as soon as possible. Therefore, a person can do it quietly, there is nothing fatal in it.
However, it is worth noting that the principle of Vibration is inviolable and extremely important. The words spoken during a Meditation or Ritual are filled with Power by Vibration precisely because they are spoken clearly with emphasis, vowel trailing and other phonetic additions that are not used in everyday speech. The Vibration method itself is provided by the Priests in the form of mp3 files specifically so that people can understand the canon of how-to's. You will hear exactly what is meant by Vibration. Saturated speech, even a person far from Spirituality will feel the Impact. Take the above into account, especially if you asked the question purely out of curiosity and not because of some life circumstances that force you to Vibrate Words quietly. Either way, it's important.
On the other hand, however, the Power of Vibrations depends more on the Operator (Magician). That is from the Mind, Will, Concentration, Purity, Speed and other factors of Soul Power. Pronunciation can not necessarily be perfect or loud, it is necessary to strive for it and to be able to control the voice correctly, it is a long process of formation. A person may shout Mantras all over the house and face failure or low efficiency from the Working, or may not shout, thus getting a high result of the Working. Over time the understanding develops, the ability to chant. And often the sounds are unique to Runes, Mantras or other Symbols.
By the way, this philosophy is what implies the true meaning of Soul Engraving. When the Symbols of Blessing «spill» over the Soul, as if illuminating it, infusing it with Power. Behind this is the great principle of Vibration. But everything comes with experience. You should not worry too much about it. Do everything that is within your capabilities and conditions.