In-Universe sexy voices. Husky ones are popular; breathy, low Marilyn Monroe-esque voices are iconic. For men, deep baritones with sonorous intonations often are used. Bassos are rarer but can also fit the bill. A popular variation is the "Siren Switch," where the speaker isn't nearly as sexy as their voice.
When it's not a particular person's voice, but an entire language someone finds erotic, that's Everything Sounds Sexier in French.
For a time, Marks and Spencer adverts in the UK featured a deliberately husky and erotic female voice describing almost comically lavish foodstuffs, followed by the tagline "This is not just food... this is M&S food".
Advert: This is not just food...
Charlie Brooker: (frantically undoing belt) Damn right it's not, it's food that's about to be fucked silly...
Ai Kora: Kirino has Maeda'sideal voice and secretly loves to sing karaoke, so naturally he persuades her to sing at every opportunity. Once she realises this is his fetish... *BOOM*
Koe de Oshigoto! is actually entirely about this, being centered around eroge voice acting and all.
The point of the existence of the Yaoi GenreAi no Kusabi CD dramas and some of the tracks on the soundtracks which center on eroge voice acting. One aptly titled "Dark Erogenous". The plot revolves around a defiant biker forcibly made a Sex Slave and the relationship he has with his in-universe irresistible master who's voice was also seductive. The late Kaneto Shiozawa was so impressive as Iason's sultry voice, a memorial drama album was released in his honor. Toshihiko Seki also has a track on both the Sympthy and Mix soundtracks where Riki speaks in a sensual tone about his life as a sex toy. Notable since the BGM itself didn't have this monologue when featured in the anime.
In YuYu Hakusho, when Bui speaks for the first time, Koto starts gushing over how sexy his voice is.
In Sword Art Online, during the GGO arc, Shino's voice is stated to be high-pitched and clear, and very pleasing to the mostly-male playerbase of the MMO she plays.
In Fairy Tail, Lucy gets aroused by Ichiya's voice, but she quickly gets turned off when she sees that he's a perverted, idiotic Gonk.
In X-Factor, Siryn's power allows her to manipulate her vocal cords to sound extra sexy, hypnotizing others into giving her what she wants.
In Gotham Central, Officer Tim Munroe describes Posion Ivy's voice as being like honey, and when he tries to imagine what she looks like based on her voice his narration trails off.
The Andromeda Strain. Dr. Hall comments that the voice of the woman making PA announcements is sexy, but the doctor is told that she's 63 years old.
Brie Larson as Envy Adams in Scott Pilgrim Vs The World puts on a constantly-aroused voice which she drops after Scott defeats Todd. Other cast members even comment on it in the DVD.
Wayne's World 2 has the boys admiring the smooth-talking Handsome Dan. Later, they promote Wayne-stock on his radio show and...well, let's just say that smooth voice is Harry Shearer.
Korean film 200 Pounds Beauty has the main character Hanna who is obese but has an amazing voice. She provides vocals for the pretty but mean Ammy and as another job, she is a phone sex employee. Then again, she was played by the gorgeous Kim Ah Joong, who did all of her singing in the movie.
Beaufort by Ron Leshem. The IDF soldiers complain that the female radio operatives with the sexiest voices inevitably turn out to be not-so-good looking.
Discworld: The book Sourcery describes Conina's voice as "the sort of voice that could make 'good morning' sound like an invitation to bed".
Daisy in The Great Gatsby is almost exclusively defined by having a sexy voice and laughter that evokes money and high class.
When George Smiley asks unhappily retired Connie Sachs for information about a Russian agent, one of the things she recalls is his wonderful voice, which she heard on surveillance tapes of phone calls.
Louis Wu meets Nessus for the first time in Ringworld:
Had Louis visualized a woman to go with that voice, she would have been Cleopatra, Helen of Troy, Marilyn Monroe, and Lorelei Huntz rolled into one. "Tanj!" The curse seemed more than usually appropriate. There Ain't No Justice! That such a voice should belong to a two-headed alien of indeterminate sex!
The aged, smallpox scarred former courtesan in The Red Pavilion has an unbelievable beautiful and sexy voice that the Judge finds extremely disturbing.
Black Dagger Brotherhood: Lover Eternal has Mary the suicide hotline operator whose voice is so appealing that John calls every night just to hear her talk (even though he is mute) and it literally bespells Rhage, her love interest.
Herman Wouk'sThe Hope, Zev Barak takes a phone call from Emily Cunningham. Barak notes a Talmud saying, "A woman's voice is naked sex," and then says this was especially true with Emily.
Dragonriders of Pern: Jaxom first falls in love with Sharra's voice, described as being low and sexy, when she was treating him for Firehead fever. She turns out to be fairly pretty, not particularly beautiful, although she certainly thinks she doesn't live up to the image he had built in his head. He likes her anyway.
Harry invoke this trope with several women, including Susan, and in the first book, Storm Front, Linda Randall's voice ON A PHONE is enough to make him reflexively ask if she's naked.
When Lara Raith puts a gun to his head and orders him to stop menacing Thomas, Harry's thought that "Wow, her voice is hot" is so strong that the downsides of getting shot are more of an afterthought. Lara is a succubus, so it's sort of expected that she'd have this.
There's a subversion in the Agatha Christie novel The Moving Finger where a character is described as incredibly attractive, but her voice is flat, dull and uninteresting, so much so that it completely ruins the narrator's idea of her as perfect.
In The Andromeda Strain, the voice that awakens the main character up after his first night of sleep at the subterranean compound is very sensual. The main character becomes a bit embarrassed when he learns the voice belongs to a seventy-two year old woman.
Ambrosio's first sermon in The Monk is clearly presented as an example as he's got half of Madrid swooning in his church.
Rex Miller's Hot Blood tale "The Voice" features a radio host finally meeting his frequent caller with her erotic voice. It's what he's always dreamed of until he finds out that half of her face was burned off in a fire.
Spenser has run into the "Siren's Switch" variation twice, once in Mortal Stakes with a Red Sox game announcer, and another time with a radio host in Crimson Joy. Both have rich, professional voices, but are extremely overweight men, and neither are particularly nice - one is just a jerk, while the other is actively villainous.
In Jane Eyre, Jane describes Mr Rochester's voice as fine and mentions several times that he's a good singer. She wants him to sing for her (to avoid being too intimate in conversation), and he asks if she likes his voice. She says she's not usually fond of pampering his vanity, but she would soothe and stimulate it when she has other motives.
Live Action TV
One episode of Taxi had Alex dating a woman from an answering service. She was overweight and had a history of men dating her because of her sexy voice and then dumping her as soon as they found what she looked like.
NCIS: Perky Goth Abby Sciuto once went under cover at a telephone sex line. She was chosen for the assignment because of her distinctly raspy voice. Played with by one of the co-workers definitely, and knowingly being separate from her voice. She even grins at Abby after a questioning look.
In Blackadder Goes Forth, a nurse who has just slept with Edmund says how she feels that men should smoke for this reason.
The Seinfeld episode "The Tape" revolves around this. Elaine leaves a provocative message on Jerry's answering machine as a joke. Only George knows it's actually Elaine. Awkwardness ensues, along with hilarity.
Peter Sellers in The Goon Show occasionally voiced a character called "breathy Kensington thing". It's a spookily realistic sexy female impersonation, often accompanied by gags about censorship.
In the first episode of The New WKRP in Cincinnati the new head of programming listens to some audition tapes; one is a very sexy woman. He is advised by several people that "the sexier the voice the uglier the person" (or words to that effect). He hires the woman sight unseen anyway, and it turns out she's Tawny Kitaen.
In one episode of the Bionic Woman remake, advantage was taken of Michelle Ryan's real-life accent for an undercover mission her character was sent out on... the techie talking to her via an electronic earpiece commented on how hot she sounded.
On Friends, Phoebe got a cold and was excited about her "new sexy voice".
The siren switch takes place in Married... with Children, when Peggy's mother (a fat, hideous redneck woman never actually seen) starts working for a sex line as "Butter." Al is horrified at first, until the money starts rolling in and he tricks his friends into calling her. When they were all hanging out at the house, she recognizes their voices from upstairs and reveals herself to them, much to their shock.
In an episode of Black Books, Fran once dated a man (Peter Serafinowicz) whom she hates simply because his voice turns her on. When she finds out that he is now doing the nightly shipping forecasts on the radio, she listens to it as a form of porn, then phones him after its over.
In one episode of Family Matters, Laura has a quite sexual reaction to the voice of an R & B Singer.
In 15 Storeys High, one character is seen on the phone angrily complaining that the delivery of his fridge is late. All is forgiven after a few soothing words from one of the call centre's staff, and he walks away from the phone satisfied... and very stiffly...
In Arrested Development, Lucille Two is aroused by Gob (Will Arnett) reading a menu in a restaurant in a deep voice.
An episode of Night Court had a group of old ladies as defendants in one case. They turned out to be very talented operators at a phone sex line, whom Dan tries (unsuccessfully) to deny recognizing when they turn on their work voices.
On Frasier, a caller admitted that she listened to Frasier's radio show because she got off to the sound of his voice.
In Boston Legal, Shirley Schmidt is able to give Denny Crane a boner (and possibly more) just by whispering his name.
In the Modern Family episode "Truth Be Told", Claire discovers that Phil has been corresponding with his ex-girlfriend Denise on Facebook. Phil insists that nothing untoward is going on and gives Claire all of Denise's messages to read. Claire reads them out loud in a sexy voice, much to Phil's confusion. Later, Denise visits and says that she thought Phil wanted to have an affair, quoting from his messages to her in a very similar sexy voice.
Jade of Victorious has a really lovely singing voice. So much that one of her classmates Andre ends up developing a crush on her because of it.
Buffy the Vampire Slayer. Veruca enraptures Oz with her husky singing voice — an annoyed Willow later describes her thus; "dresses like Faith, voice like an albatross".
The X-Files episode "Small Potatoes" features Chantal's message on Mulder's answering machine: "Hello, Marty? Chantal. It's been so long since we've spoken and I've been so lonely not hearing your sexy voice." Considering that Chantal is a phone sex operator, one must take it with a pinch of salt.
"Now I know why he's been holding back. If he spoke, he'd be buried under a pile of panties and roses."
A ludicrous example occurs in Step by Step, where the girls are all infatuated with the voice of the guy who answers the phone at the pizzeria, so Al asks him on a blind date. It turns out the guy is fat, and the rest of the episode deals with that. But as soon as you see the guy, they completely drop the notion that he had a sexy voice. Instead, he sounds like a cartoon fat guy. (In fact he sounds a lot like Chris Farley, which the episode even explicitly acknowledges.) What happened?
Castle: In "Cops and Robbers", Trapper John describes Detective Kate Beckett as having a "bedroom voice."
The Big Bang Theory: Bernadette and Howard are dog-sitting for Raj and they lose the dog. While out searching for it, they decide they should call the dog's name using Raj's accent, leading to this Ho Yay-packed exchange:
Howard: When this all blows over, remember that voice. Itís kind of a turn-on.
Bernadette: It turns you on when I sound like Raj?
On an episode of Murphy Brown, one of Murphy's many, many secretaries was a mousy, buttoned-up, librarian-looking woman named Patricia. She starts out OK, but once Murphy leaves the room while Patricia's taking a call, she turns around, drops her voice an octave, and in the middle of the FYI newsroom starts her second career as a phone sex operator under the alias "Bambi." Later on, when Murphy finds out, and tells the guy on the phone that Bambi was sent back to the forest and she was Thumper, she talks to him for a second, then monotonously starts saying, "I'm hot, I'm on fire, oh boy, oh baby, oh baby," which, [[Squick judging by her reaction,]] still did the trick.
The Trope Maker and Ur-Example are the Sirens from The Odyssey who were said to lead men to their deaths by their heavenly singing, and they have been referenced (and parodied) in countless other works of fiction for ever.
Odysseus was described by Helen to have appealing voice during The Iliad.
In Hindu Mythology, Hanuman's voice is said to be so potent that he could impregnate women just by singing.
A "siren switch" shows up in the music video for the re-release of Aerosmith's "Sweet Emotion", in which a young man calls a sex hotline and is drawn in by the sultry female voice on the other line. At the end of the video, we finally see the conversation from her end: she's a chunky middle-aged woman in a drab housedress holding a baby in one hand, ironing with the other, and gripping the phone with her shoulder.
The Y-O-U song "Radio" is about all about a girl getting uncontrollably turned on by rock music.
On their fifth album, Cardiology, Good Charlotte has a song called "Sex on the Radio" whose narrator is in a relationship with a radio personality. So titled because the girl's voice sounds like, well, sex on the radio.
Dream Theater's "Home" heavily implies a sex scene about halfway through, complete with a woman moaning in the background.
Papa Roach's "The Addict" features a woman moaning rather suggestively after the bridge-y bit.
The late Seventies cover of "Wild Thing" by one-hit-wonder Fancy is characterized by the group's Playboy Playmate lead singer gasping and moaning her way through the lyrics.
"Oooooooh.... love to love you, baby. OOOOOOOH.... love to love you, baby." Repeat ad nauseam for seventeen minutes. This song not only launched Donna Summer to stardom, but led the Catholic Church to declare the song as the work of Satan. A popular rumor is that Donna induced her own orgasms while recording the song, but she says it was all an act.
Dean Ambrose (aka indie standout Jon Moxley) of WWE's The Shield has a very sexy, unique, slightly raspy voice that is mesmerizing to listen to.
Made fun of in Rayman 3: Hoodlum Havoc, where Globox falls for the voice of an unknown female character inside the Hoodlum HQ. This helps the Hoodlums lure him into a trap.
An unknown character in an optional scene in Final Fantasy IX keeps Zidane interested from the other side of a stone gate with her voice. The speaker is never revealed, but, given that it was a gate to the Burmecian territories, the odds are that she was a Petting Zoo Person.
In Psychonauts there is an underground cart that works as a quick-travel device. Whenever Raz wants to use it, he'll be greeted by a deliberately erotic computerized female voice that will ask him where he wants to go. If the player does not want to go anywhere, Raz will humorously answer that he just dropped by to listen to her voice.
In Double Fine's game The Cave, Stephen Stanton plays the titular talking cave, who lampshades his alluring voice in his very first line.
Shepard, Samantha, and the guys who built her all comment on EDI (the Normandy's sentient computer) having a sexy voice.
In the Citadel DLC it is revealed that Traynor didn't only find EDI's voice sexy—she was genuinely aroused by it, wanting to do some very naughty things with it.
In the Citadel DLC, Garrus refers to his voice as one of his good points twice when faking a first date with Shepard. And it's possible he does it for Shepard's benefit; Shepard admits that his voice is what she misses the most if he dies in the Suicide Mission in the second game.
Shepard: Is that supposed to melt a girl's heart?
Garrus: No. But this voice is...
After a mission in which the good guys hijack an intergalactic radio station to expose the Big Bad Mengsk's crimes in Starcraft II Wings Of Liberty, this trope comes up in a bonus conversation in thecantina. Responding to Tychus' enthusiasm for a job well done, Jim Raynor humorously asks if he'll quit to do radio full time. Laughing, Tychus replies, "Naww, regular folks just ain't read for the raw sex appeal I'd unleash on their grey little lives."
In Act III of Diablo III, the demon lord Azmodan sics his consort, Cydaea on the player. Voiced by none other than Claudia Black, her title is "Maiden of Lust."
In the beginning of the BL sci-fi Dramatical Murder, the protagonist Aoba is introduced essentially weaponizing a particular seductive tone to his voice over the phone to get more sales for the shop he works at, as people will call back just to hear it again, and wind up buying more as a result. Most of his companions also comment on its supposed beguiling quality at some point, although only the resident Cloud Cuckoolander gives hints towards its true nature. It's later revealed that he in fact has a Compelling Voice that can influence the will of individualsnote Despite being Yaoi Genre, its focus is on the sci-fi and romance, and the influencing of will is done at dramatic instances, such as when someone is about to preform a Heroic Sacrifice., and when put in dire circumstance in which greater powers manifest (i.e. he or someone he holds dear is threatened), his oft-staticking-on-screen Super-Powered Evil Side will take over as he blacks out, usually curb-stomping everything in its wake thereafter, sometimes with fatality.
There's a Running Gag in Hey Ash, Whatcha Playin'? based around Ashley's crush on David Hayter based on the voice he uses for Solid Snake. In one montage, there's a short clip of her being caught masturbating to a recording of him, and in one video a whiteboard showing a complicated plan has a picture of Hayter on it, surrounded by little hearts. When David Hayter leaves her a voice mail message, she screams.)
Cecil of Welcome To Night Vale has described Carlos's voice as "oaky", and "like caramel". The audience has, as of The Phone Call heard him, and can now decide for themselves.
A rich widow in the Woody Woodpecker cartoon, "A Fine Feathered Frenzy" pulls the siren switch. Woody reads her ad in the personals where it says that she's a 'Gorgeous Gal' who is wealthy, has lots of food and is looking to marry a young man. So he calls her on the phone. With her sexy voice Gorgeous calls him sweetie and dream boy, says she loves Woodpeckers and he's the only thing on her mind. She invites him to come over to her mansion and says she'll be waiting for him. When Woody meets her it turns out she is an overweight and elderly crow. Gorgeous Gal chases after him, lavishes him with kisses and continues flirting with him with her lovely voice. Woody is no longer interested but Gorgeous Gal's love for woodpeckers wins out in the end. She drags him into a submarine and gets a priest to marry them.
Medusa performs the siren switch in Captain N: The Game Master during the episode, "Mega Trouble For Megaland". Kid Icarus pulls Simon Belmont's goggles over his eyes and covers them with black paint so he doesn't look at Medusa while they are on a mission. She flirts with Simon telling him he's handsome and that there's a chance she could fall for him. Her voice is so alluring that Simon is ready to kiss her, sight unseen. Of course when he does take his goggles off to look at Medusa he sees that she has light blue skin, large yellow reptilian eyes, the body and figure of an unattractive elderly woman and snakes for hair. The horrified Simon turns to stone.
In "To Live and Die in Dixie", Stewie joins a bluegrass band and sings this little ditty:
Met her on the CB, said her name was Mimi,
Sounded like an angel come to Earth (Come to Earth)
But when I went to meet her, man you should have seen her.
Twice as tall as me, three times the girth (Giiiiirth)
An episode had Lois become irresistibly attracted to the low voice Peter develops due to illness.
One episode of Duckman has Our Intrepid Hero fall in love with a female 911 operator because of how her voice sounded. Then he finally meets her in person and discovers that she's a bit lackingin the looks department. So much so, that her face isn't even shown onscreen until she has drastic cosmetic surgery to make herself look pretty. And she's literally perfect after this. She had the voice and the personality, but after the surgery, she had the total package. At this point, Duckman (who had still loved her despite her appearance) realizes that she's too good for him and he dumps her so she can find someone better.
The Dexters Laboratory episode "Voice Over" had Dexter swapping his computer's voice in an attempt to fix it. One of them was probably the most seductive voice ever heard in a children's cartoon. He had to change it because he couldn't stop sweating.