To hide sth/sb by changing their appearance,sound

Disguise
To change your appearance,sound or taste etc of something, especially in order to hide your appearance:

- She has had a lot of cosmetic surgery in an attempt to disguise her age.
- We went the party in disguise.
- There's no way you can disguise that southern accent.

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Camouflage
To conceal from an enemy by the use of disguise or by protective coloring, leaves, branches, paints and clothes that make it look like the things around it.

- The men were dressed in camouflage and carrying automatic weapons.
- They were Wearing flamboyant orange berets and somber brown camouflage uniforms.
- They donned white armbands to distinguish themselves from the Chechens wearing similar camouflage suits.
- The whiteness of the arctic fox acts as camouflage, hiding it from its enemies.

Guise
Under/in the guise of: looking like someone or something else, or pretending to be them:

- They operated a drug-smuggling business under the guise of an employment agency.
- The company has been accused of trying to sell their products under the guise of market research.
- This is a country where reporters have to visit in the guise of tourists.
- he visited in the guise of an inspector.
- sums paid under the guise of consultancy fees.

Mask
To cover or hide something so that it can not be seen:

- The bank robbers wore masks throughout the raid.
Pretending to be somebody else.
- under the mask of being a tourist, he spied on the economic affairs of the country.

Cloak
(literary) to cover something or hide it.
Under the cloak of

- But he strongly disapproved of the proselytizing that went on under the cloak of humanitarianism.
- Lawyers, under the cloak of client confidentiality, can mask the beneficial owners of accounts.